Consolidated Statements of Cash Flows (USD $)
In Thousands, unless otherwise specified
 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Cash flows from operating activities:    
Net income $ 259,898 $ 211,067
Items not involving cash:    
Stock-based compensation 24,379 19,724
Depreciation of property and equipment 47,861 28,204
Amortization of intangible assets 162,179 147,368
Deferred lease inducements and rent 5,947 24,042
Deferred income taxes (43,546) (36,225)
Tax benefit on option exercises (4,241) (10,469)
Deferred financing cost amortization 7,126 6,999
Changes in operating assets and liabilities, net of effects from acquisitions:    
Accounts receivable (336,629) (119,630)
Rebates receivable (574,416) 11,131
Restricted cash (4) 199
Other current assets (11,390) 8,036
Accounts payable 287,949 47,608
Accrued expenses and other current liabilities 48,531 (17,983)
Rebates payable 558,770 14,022
Other long-term assets and liabilities (5,320) 1,760
Net cash provided by operating activities 427,094 335,853
Cash flows from investing activities:    
Acquisition, net of cash acquired (2,026) (7,076)
Purchases of property and equipment (46,209) (93,272)
Proceeds from restricted cash 0 20,004
Net cash used by investing activities (48,235) (80,344)
Cash flows from financing activities:    
Proceeds from issuance of debt 492,500 100,000
Repayment of long-term debt (325,000) (256,250)
Payment of financing costs (1,963) (2,347)
Proceeds from exercise of options 5,596 2,976
Proceeds from exercise of warrants 3,453 487
Tax benefit on option exercises 4,241 10,469
Payments of contingent consideration 0 (23,203)
Distributions to non-controlling interest (37,800) (22,115)
Other (353) 0
Net cash provided (used) by financing activities 140,674 (189,983)
Effect of foreign exchange on cash balances 61 (75)
Change in cash and cash equivalents 519,594 65,451
Cash and cash equivalents, beginning of period 387,241 370,776
Cash and cash equivalents, end of period $ 906,835 $ 436,227