Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net income	$ 368,707		$ 284,501	$ 216,199
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	21,097		16,885	14,116
Stock-based compensation	37,649		26,676	19,275
Provision for losses on accounts receivable	24,412		18,867	21,896
Amortization of deferred financing costs	2,796		3,276	2,279
Loss on extinguishment of debt	15,764
Amortization of intangible assets	86,149		49,313	32,376
Amortization of premium on receivables	3,259		3,263	3,265
Deferred income taxes	(41,716)		(5,453)	(3,337)
Equity method investment loss	8,586
Fair value adjustment for contingent consideration arrangements	(27,501)
Changes in operating assets and liabilities (net of acquisitions):
Restricted cash	6,625		5,430	2,088
Accounts receivable	246,465		(45,005)	(71,102)
Prepaid expenses and other current assets	2,820		(74)	(6,847)
Other assets	12,455		38,906	(46,553)
Excess tax benefits related to stock-based compensation	(56,790)		(32,535)	(29,355)
Accounts payable, accrued expenses, and customer deposits	(102,443)		11,635	(18,840)
Net cash provided by operating activities	608,334		375,685	135,460
Investing activities
Acquisitions, net of cash acquired	(2,567,017)	[1]	(728,343)	(190,447)
Purchases of property and equipment	(27,070)		(20,785)	(19,111)
Net cash used in investing activities	(2,594,087)		(749,128)	(209,558)
Financing activities
Excess tax benefits related to stock-based compensation	56,790		32,535	29,355
Repurchase of common stock				(200,000)
Proceeds from issuance of common stock	29,641		30,438	27,187
Borrowings on securitization facility, net	326,000		51,000	18,000
Deferred financing costs paid	(43,943)		(1,970)	(3,776)
Proceeds from notes payable	2,320,000			250,000
Principal payments on notes payable	(546,875)		(28,125)	(30,414)
Borrowings from revolver- A Facility	807,330		783,663	455,000
Payments on revolver- A Facility	(783,600)		(261,516)	(480,000)
Borrowings from foreign revolver- B Facility			16,715
Payments on foreign revolver- B Facility	(7,337)		(8,552)
Payments on acquired debt			(164,083)
Borrowings from swing line of credit, net	4,990			(1,874)
Other	(731)		(14,380)	(1,490)
Net cash provided by financing activities	2,162,265		435,725	61,988
Effect of foreign currency exchange rates on cash	(37,548)		(7,826)	10,600
Net increase (decrease) in cash	138,964		54,456	(1,510)
Cash and cash equivalents at beginning of year	338,105		283,649	285,159
Cash and cash equivalents at end of year	477,069		338,105	283,649
Supplemental cash flow information
Cash paid for interest	29,098		25,886	14,760
Cash paid for income taxes	$ 79,124		$ 99,308	$ 38,169

[1] Amounts reported in acquisitions and investment, net of cash acquired, includes debt assumed and immediately repaid in acquisitions.