Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Assumptions utilized in the valuation for options granted Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Statement [Line Items] Statement [Line Items] Current assets: Assets, Current [Abstract] Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current Customer relationships and other intangible assets, accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Stockholders' equity: Stockholders' Equity Attributable to Parent [Abstract] Common stock, par value Common Stock, Par or Stated Value Per Share Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares oustanding Common Stock, Shares, Outstanding Income Tax Disclosure [Abstract] Reconciliation of effective income tax rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Accounting Policies [Abstract] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Commitments and Contingencies Disclosure [Abstract] Legal Matters Legal Matters and Contingencies [Text Block] Payables and Accruals [Abstract] Accrued Expenses Accounts Payable and Accrued Liabilities Disclosure [Text Block] Document and Entity Information [Abstract] Document and Entity Information [Abstract] Entities [Table] Entities [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Entity Information [Line Items] Entity Information [Line Items] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Nationwide Traffic Services, LLC. Nationwide Traffic Services LLC [Member] Nationwide Traffic Services LLC [Member] Advantage Transport, Inc. Advantage Transport, Inc. [Member] Advantage Transport, Inc. [Member] Trailer Transport Systems Trailer Transport Systems [Member] Trailer Transport Systems [Member] Purple Plum Logistics, LLC Purple Plum Logistics, LLC [Member] Purple Plum Logistics, LLC [Member] Shipper Direct Logistics, Inc. [Member] Shipper Direct Logistics, Inc. [Member] Shipper Direct Logistics, Inc. [Member] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Selling, general and administrative expenses Selling, General and Administrative Expenses [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Acquisitions: Business Acquisition [Line Items] Acquisition purchase price Business Acquisition, Cost of Acquired Entity, Purchase Price Potential cash payment for contingent consideration Business Acquisition, Contingent Consideration, Potential Cash Payment Business Acquisition, Returned Purchase Price Business Acquisition, Returned Purchase Price Business Acquisition, Returned Purchase Price Goodwill amount from acquisition Business Acquisition, Purchase Price Allocation, Goodwill Amount Goodwill related to contingent consideration Business Acquisition, Contingent Consideration, Goodwill Related to Contingent Consideration Business Acquisition, Contingent Consideration, Goodwill Related to Contingent Consideration Cash paid for contingent consideration Business Acquisition, Contingent Consideration, Cash Paid Business Acquisition, Contingent Consideration, Cash Paid Change in contingent consideration due to seller Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Contingent conisderation due to seller Business Acquisition, Contingent Consideration, at Fair Value as of the Balance Sheet Date Business Acquisition, Contingent Consideration, at Fair Value as of the Balance Sheet Date Potential cash payment for contingent consideration, undiscounted Business Acquisition, Contingent Consideration, Potential Cash Payment, Undiscounted Business Acquisition, Contingent Consideration, Potential Cash Payment, Undiscounted Amount of goodwill deductible for U.S. income tax purposes Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount Preliminary purchase price Business Acquisition, Cost of Acquiring Entity, Preliminary Purchase Price Business Acquisition, Cost of Acquiring Entity, Preliminary Purchase Price Preliminary potential cash payment Business Acquisition, Contingent Consideration, Preliminary Potential Cash Payment Business Acquisition, Contingent Consideration, Preliminary Potential Cash Payment Percentage of ownership acquired Business Acquisition, Percentage of Voting Interests Acquired Fair Value Disclosures [Abstract] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value, Measurements, Recurring Fair Value, Measurements, Recurring [Member] Asset Class [Axis] Asset Class [Axis] Fair Value by Asset Class [Domain] Fair Value by Asset Class [Domain] Money market funds Money Market Funds [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value, Measurements, Fair Value Hierarchy [Domain] Total Estimate of Fair Value, Fair Value Disclosure [Member] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] RGA RGA [Member] RGA [Member] DSI DSI [Member] DSI [Member] Lubenow Lubenow [Member] Lubenow [Member] Freight Management, Inc. [Member] Freight Management, Inc. [Member] Freight Management, Inc. [Member] Advantage Transport, Inc. [Member] Liability Class [Axis] Liability Class [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Contingent consideration Contingent Consideration [Member] Contingent Consideration [Member] Fair value measurement: Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Probability rate of paying the contingent consideration Business Acquisition, Contingent Consideration, Probability of Payment Business Acquisition, Contingent Consideration, Probability of Payment Discount rate used to determine fair value of contingent consideration Business Acquisition, Contingent Consideration, Discount Rate Used to Determine Fair Value Business Acquisition, Contingent Consideration, Discount Rate Used to Determine Fair Value Assets: Assets, Fair Value Disclosure [Abstract] Money market funds Cash and Cash Equivalents, Fair Value Disclosure Liabilities: Liabilities, Fair Value Disclosure [Abstract] Contingent consideration obligation Obligations, Fair Value Disclosure Reconciliation of the beginning and ending balances of the liabilities measured at fair value Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Balance at beginning of period Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value Increase related to purchase accounting for acquisitions Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease) From Acquisition Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease) From Acquisition Change in fair value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease) Payment of contingent consideration Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Balance at end of period Income Taxes Income Tax Disclosure [Text Block] Accrued compensation Accrued Salaries, Current Accrued rebates Accrued Rebates, Current Accrued Rebates Deferred rent Deferred Rent Credit, Current Other Other Accrued Liabilities, Current Total accrued expenses Accrued Liabilities, Current Assets Assets [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Accounts receivable, net of allowance for doubtful accounts of $2,292,271 and $3,017,742 at September 30, 2012 and December 31, 2011, respectively Accounts Receivable, Net, Current Income taxes receivable Income Taxes Receivable, Current Prepaid expenses Prepaid Expense, Current Other current assets Other Assets, Current Total current assets Assets, Current Property and equipment, net Property, Plant and Equipment, Net Intangible assets: Intangible Assets Including Goodwill [Abstract] Intangible assets including goodwill [Abstract] Goodwill Goodwill Intangible assets, net of accumulated amortization of $8,051,186 and $6,563,870 at September 30, 2012 and December 31, 2011, respectively Intangible Assets, Net (Excluding Goodwill) Other assets Other Noncurrent Assets Other Noncurrent Assets Total assets Assets Liabilities and stockholders' equity Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Trade, Current Current maturities of capital lease obligations Capital Lease Obligations, Current Due to seller-short term Business Acquisition Contingent Consideration at Reporting Period Fair Value Current Current portion of the fair value, as of the financial statement date, of potential payments under the contingent consideration arrangement, including cash and shares as applicable. Accrued expenses Income tax payable Accrued Income Taxes, Current Deferred income taxes Deferred Tax Liabilities, Net, Current Total current liabilities Liabilities, Current Due to seller-long term Business Acquisition Contingent Consideration at Reporting Period Fair Value Noncurrent Noncurrent portion of the fair value as of the acquisition date of potential payments under the contingent consideration arrangement, including cash and shares as applicable. Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Capital lease obligations, net of current maturities Capital Lease Obligations, Noncurrent Total liabilities Liabilities Common stock, par value $0.0001 per share, 100,000,000 shares authorized, 22,389,487 and 22,155,857 shares were issued and outstanding at September 30, 2012 and December 31, 2011, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Total stockholders' equity Stockholders' Equity Attributable to Parent Total liabilities and stockholders' equity Liabilities and Equity Earnings Per Share [Abstract] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Stock options Stock Options [Member] Anti-dilutive sercurities excluded from the calculation of earnings per share: Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Stock options excluded from the calculation of diluted earnings per share Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Net income Net Income (Loss) Attributable to Parent Denominatior for basic earnings per share-weighted-average shares Weighted Average Number of Shares Outstanding, Basic Employee stock options/Unvested Restricted Stock Weighted Average Number Diluted Shares Outstanding Adjustment Denominator for dilutive earnings per share Weighted Average Number of Shares Outstanding, Diluted Basic net income per common share Earnings Per Share, Basic Diluted net income per common share Earnings Per Share, Diluted Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Customer relationships Customer Relationships [Member] Non-compete agreements Noncompete Agreements [Member] Trade names Trade Names [Member] Intangible assets: Finite-Lived Intangible Assets [Line Items] Summary of amortizable intangible assets: Finite-Lived Intangible Assets, Net [Abstract] Finite-lived intangible assets, gross Finite-Lived Intangible Assets, Gross Less accumulated amortization Intangible assets, net Finite-Lived Intangible Assets, Net Weighted average useful life Finite-Lived Intangible Asset, Useful Life Amortization of expense Amortization of Intangible Assets Estimated amortization expense for hte next five years and thereafter: Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract] Remainder of 2012 Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year 2013 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2014 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2015 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2016 Finite-Lived Intangible Assets, Amortization Expense, Year Five Thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Roll-forward of goodwill Schedule of Goodwill [Table Text Block] Summary of amortizable intangible assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Estimated amortization expense for the next five years and thereafter Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Acquisitions Business Combination Disclosure [Text Block] Statement of Cash Flows [Abstract] Operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Deferred income taxes Deferred Income Tax Expense (Benefit) Noncash stock compensation expense Share-based Compensation Reduction in contingent consideration due to seller Depreciation and amortization Depreciation, Depletion and Amortization Change in assets, net of acquisitions: Increase (Decrease) in Operating Assets [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Taxes receivable (payable) Increase (Decrease) in Income Taxes Payable, Net of Income Taxes Receivable Prepaid expenses and other assets Increase (Decrease) in Prepaid Expense and Other Assets Change in liabilities, net of acquisitions: Increase (Decrease) in Operating Liabilities [Abstract] Accounts payable Increase (Decrease) in Accounts Payable Accrued expenses and other Increase (Decrease) in Other Operating Liabilities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Short-term note receivable Payments to Acquire Notes Receivable Payments for acquisitions, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Principal payments on capital lease obligations Repayments of Long-term Capital Lease Obligations Tax benefit of stock options exercised Tax Benefit from Stock Options Exercised Payment of contingent consideration Payments of Merger Related Costs, Financing Activities Issuance of shares, net of issuance costs Proceeds from Issuance of Common Stock Employee tax withholdings related to net share settlements of equity-based awards Payments Related to Tax Withholding for Share-based Compensation Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Increase in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Supplemental disclosure of cash flow information Supplemental Cash Flow Information [Abstract] Cash paid during the period for interest Interest Paid Cash paid during the period for income taxes Income Taxes Paid Non-cash financing activity Non Cash Financing Activity [Abstract] Non Cash Financing Activity [Abstract] Vesting of restricted shares Stock Issued During Period, Shares, Restricted Stock Award, Gross Due to seller Contingent Earnout Payments Increase Due to New Acquisitions Contingent Earnout Payments, Increase Due to New Acquisitions Financial liabilities measured at fair value on a recurring basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Reconciliation of the beginning and ending balances for the liabilities measured at fair value using significant unobservable inputs Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Earnings Per Share Earnings Per Share [Text Block] Fair Value Measurement Fair Value Disclosures [Text Block] Components of accrued liabilities Schedule of Accrued Liabilities [Table Text Block] Loss Contingencies [Table] Loss Contingencies [Table] Litigation Status [Axis] Litigation Status [Axis] Litigation Status [Domain] Litigation Status [Domain] Threatened litigation Threatened Litigation [Member] Settled litigation Settled Litigation [Member] Settled Litigation [Member] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Collectibility of receivables Collectibility of Receivables [Member] Unasserted claim Unasserted Claim [Member] General and administrative expenses General and Administrative Expense [Member] Legal matters: Loss Contingencies [Line Items] Estimate of possible loss Loss Contingency, Estimate of Possible Loss Amount of possible loss Loss Contingency, Range of Possible Loss, Maximum Litigation settlement amount Litigation Settlement, Gross Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Award Type [Domain] Award Type [Domain] Restricted stock Restricted Stock [Member] Stock based compensation plans: Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Stock-based compensation expense Allocated Share-based Compensation Expense Tax benefits from stock-based compensation expense Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Grants in period, options Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Grants in period, other than options Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Assumptions utilized in the valuation for options granted: Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] Dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Risk-free interest rate, minimum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum Risk-free interest rate, maximum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum Weighted-average expected life Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Volatility, minimum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum Volatility, maximum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum Income Statement [Abstract] REVENUE Transportation Services Revenue The total dollar amount of transportation and transportation-related services charged to customers during the period. COSTS AND EXPENSES: Costs and Expenses [Abstract] Transportation costs Cost of Purchased Transportation and Related Services The total costs of purchased transportation and transportation-related services to meet customer needs during the period. Selling, general, and administrative expenses Selling, General and Administrative Expense INCOME FROM OPERATIONS Operating Income (Loss) Interest income Investment Income, Interest Interest expense Interest Expense, Debt Other expense Other Nonoperating Income (Expense) OTHER EXPENSE, NET Other Expense Other Expense is the aggregate of interest income, interest expense, and other income and expenses. INCOME BEFORE PROVISION FOR INCOME TAXES Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest INCOME TAX EXPENSE Income Tax Expense (Benefit) NET INCOME Basic net income per share Diluted net income per share Preparation of Financial Statements and Use of Estimates Use of Estimates, Policy [Policy Text Block] Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Affiliated entity Affiliated Entity [Member] InnerWorkings InnerWorkings [Member] InnerWorkings [Member] Groupon Goods Groupon Goods [Member] Groupon Goods [Member] Immediate family member of management or principal owner Immediate Family Member of Management or Principal Owner [Member] Lefkofsky & Gorosh, P.C. Lefkofsky Gorosh [Member] Lefkofsky Gorosh [Member] Related parties: Related Party Transaction [Line Items] Company shares owned by affiliated entities Common Stock, Shares Owned By Related Parties Common Stock, Shares Owned By Related Parties Percentage of total shares outstanding owned by affiliate Percentage of Total Shares Outstanding Owned by an Affiliated Entity Percentage of Total Shares Outstanding Owned by an Affiliated Entity Revenue from transactions with related party Revenue from Related Parties Due from related parties Due from Related Parties Due to related parties Due to Related Parties Amounts of transaction with related party Related Party Transaction, Amounts of Transaction New Accounting Pronouncements and Changes in Accounting Principles [Abstract] New Accounting Pronouncements Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Stock Based Compensation Plans Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Computation of basic and diluted earnings per common share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] Statement of Stockholders' Equity [Abstract] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock [Member] Additional Paid-in Capital [Member] Retained Earnings [Member] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Common stock, shares at beginning of period Stockholders' equity at beginning of period Share compensation expense Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Exercise of stock options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercise of stock options Stock Issued During Period, Value, Stock Options Exercised Common stock issued for vested restricted stock (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Common stock issued for vested restricted stock Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Common shares withheld and retired to satisfy employee tax witholding obligations upon vesting of restricted stock (in shares) Shares Paid for Tax Withholding for Share Based Compensation Common shares withheld and retired to satisfy employee tax witholding obligations upon vesting of restricted stock Adjustments Related to Tax Withholding for Share-based Compensation Tax benefit from the exercise of stock options Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation Common stock, shares at end of period Stockholders' equity at end of period Income before provision for income taxes Income tax expense Effective tax rate Effective Income Tax Rate, Continuing Operations Related Parties Related Party Transactions Disclosure [Text Block] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Goodwill: Goodwill [Line Items] Goodwill roll-forward: Goodwill [Roll Forward] Balance at beginning of period Goodwill acquired related to the purchase of business Goodwill, Acquired During Period Balance at end of period