CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Operating activities:    
Net income (loss) $ (6,127) $ 9,740
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:    
Depreciation 4,188 3,540
Amortization 13,625 6,311
Amortization of debt issuance costs 827 710
Impairment loss 1,402 1,053
Excess tax benefit from stock-based compensation (2,095) (23,429)
Stock-based compensation expense 7,442 7,879
Deferred income tax benefit, net 3,886 5,090
Provision for losses on accounts receivable 1,558 986
Changes in operating assets and liabilities:    
Accounts receivable (8,640) (12,499)
Prepaid expenses and other current assets (566) (1,509)
Deposits and other assets (83) 39
Accounts payable and other liabilities 13,231 (5,991)
Deferred revenue 1,521 1,525
Net cash provided by (used in) operating activities 30,169 (6,555)
Investing activities:    
Proceeds from sale and settlement of investments 650 0
Purchases of property and equipment and other assets (11,744) (4,149)
Net cash used in investing activities (11,094) (4,149)
Financing activities:    
Payments of long-term debt (5,000) (4,375)
Payments of deferred consideration 0 (1,344)
Excess tax benefit from stock-based compensation 2,095 23,429
Repurchase of restricted stock to satisfy tax withholding obligations (5,203) (42,555)
Proceeds from exercise of stock options and employee stock purchase plan 4,055 3,001
Net cash used in financing activities (4,053) (21,844)
Effect of foreign currency exchange rates on cash and cash equivalents (263) 38
Net increase (decrease) in cash and cash equivalents 14,759 (32,510)
Cash and cash equivalents at the beginning of period 527,012 255,953
Cash and cash equivalents at the end of period $ 541,771 $ 223,443