Business Combinations Catalyst (Details) (USD $)
 0 Months Ended 1 Months Ended 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 6 Months Ended 0 Months Ended
Sep. 06, 2012
Oct. 31, 2012
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Catalyst
Jun. 30, 2013
Catalyst
Jul. 02, 2012
Catalyst
Jun. 30, 2012
Common Stock
Jul. 02, 2012
Common Stock
Catalyst
Jul. 02, 2012
Initial Amounts Recognized at Acquisition Date
Catalyst
Jul. 02, 2012
Prior Measurement Period Adjustments
Catalyst
Jul. 02, 2012
Current Measurement Period Adjustments
Catalyst
Merger Agreement [Abstract]                            
Stock conversion, share received per share converted                     1.3212      
Stock conversion, cash received per share converted, prior to stock split                     0.6606      
Number of common shares received after stock split 2 2                        
Stock conversion, cash received per share converted                 $ 28.00          
Shares issued                   11,960,000 66,800,000      
Warrants issued                     500,000      
Revenue from acquired company included in consolidated statement of operations             $ 1,700,000,000 $ 3,300,000,000            
Goodwill expected to be tax deductible                 525,000,000          
Amortization of intangible assets     50,092,000 9,011,000 100,148,000 19,330,000 43,000,000 86,000,000            
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year     94,400,000   94,400,000   80,100,000 80,100,000            
Fair value of intangible assets             1,200,000,000 1,200,000,000            
Customer relationships, weighted average useful life               9 years            
Business Acquisition, Cost of Acquired Entity, Purchase Price [Abstract]                            
Cash paid to shareholders                 1,415,276,000          
Fair value of common shares issued                 3,238,141,000 [1]          
Fair value of warrants and stock options issued                 19,824,000 [2]          
Total purchase price                 4,673,241,000          
Business Acquisition, Purchase Price Allocation, Assets Acquired (Liabilities Assumed), Net [Abstract]                            
Cash and cash equivalents                 93,460,000     93,775,000 [3] (315,000) [4] 0 [5]
Other current assets                 703,545,000     695,888,000 [3] 5,202,000 [4] 2,455,000 [5]
Total current assets                 797,005,000     789,663,000 [3] 4,887,000 [4] 2,455,000 [5]
Goodwill                 4,032,697,000     4,010,235,000 [3] 8,492,000 [4] 13,970,000 [5]
Customer relationships intangible                 1,184,800,000     1,184,800,000 [3] 0 [4] 0 [5]
Other long-term assets                 88,729,000     87,174,000 [3] 1,547,000 [4] 8,000 [5]
Total assets acquired                 6,103,231,000     6,071,872,000 [3] 14,926,000 [4] 16,433,000 [5]
Accounts Payable                 338,824,000     338,819,000 [3] 0 [4] 5,000 [5]
Pharmacy benefit management rebates payable                 177,776,000     176,202,000 [3] 2,935,000 [4] (1,361,000) [5]
Accrued expenses and other current liabilities                 192,384,000     187,851,000 [3] 1,348,000 [4] 3,185,000 [5]
Long-term debt                 311,994,000     311,994,000 [3] 0 [4] 0 [5]
Other long-term liabilities                 410,622,000     385,375,000 [3] 10,643,000 [4] 14,604,000 [5]
Total liabilities assumed                 1,431,600,000     1,400,241,000 [3] 14,926,000 [4] 16,433,000 [5]
Non-controlling interest                 (1,610,000)     (1,610,000) [3] 0 [4] 0 [5]
Net assets acquired                 $ 4,673,241,000     $ 4,673,241,000 [3] $ 0 [4] $ 0 [5]
[1] Valued based on the number of outstanding shares immediately prior to the Merger multiplied by the exchange ratio of 1.3212 (0.6606 prior to the October 2012 two-for-one stock split), multiplied by the closing market price of Catamaran shares on July 2, 2012.
[2] The Black-Scholes pricing model was used to calculate the fair value of the replacement warrants and stock options issued.
[3] As previously reported in the Company's Form 10-Q for the period ended September 30, 2012.
[4] These measurement period adjustments were recorded to reflect an additional $1.0 million paid to the former HealthTran owners for the working capital reconciliation and changes in the estimated fair values of the associated assets acquired and liabilities assumed based on factors existing as of the acquisition date.
[5] These represent measurement period adjustments during the six months ended June 30, 2013 and were recorded to reflect changes in the estimated fair values of the associated assets acquired and liabilities assumed based on factors existing as of the acquisition date.