Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities
Net income	$ 216,199,000	$ 147,335,000	$ 107,896,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	14,116,000	11,451,000	11,261,000
Stock-based compensation	19,275,000	21,743,000	26,755,000
Provision for losses on accounts receivable	21,896,000	19,226,000	18,883,000
Amortization of deferred financing costs	2,279,000	1,864,000	2,016,000
Amortization of intangible assets	32,376,000	19,590,000	17,205,000
Amortization of premium on receivables	3,265,000	3,266,000	3,263,000
Deferred income taxes	(3,337,000)	(2,920,000)	(3,952,000)
Loss on early extinguishment of debt		2,669,000
Changes in operating assets and liabilities (net of acquisitions):
Restricted cash	2,088,000	6,579,000	5,639,000
Accounts receivable	(71,102,000)	(80,024,000)	(38,960,000)
Prepaid expenses and other current assets	(6,847,000)	17,581,000	(3,506,000)
Other assets	(46,553,000)	(1,935,000)	63,000
Excess tax benefits related to stock-based compensation	(29,355,000)	(13,727,000)	(10,710,000)
Accounts payable, accrued expenses, and customer deposits	(18,840,000)	126,927,000	3,902,000
Net cash provided by operating activities	135,460,000	279,625,000	139,755,000
Investing activities
Acquisitions, net of cash acquired	(190,447,000)	(333,763,000)	(10,022,000)
Purchases of property and equipment	(19,111,000)	(13,454,000)	(11,194,000)
Net cash used in investing activities	(209,558,000)	(347,217,000)	(21,216,000)
Financing activities
Excess tax benefits related to stock-based compensation	29,355,000	13,727,000	10,710,000
Net proceeds from initial public offering			9,560,000
Payment of dividends on convertible preferred stock			(7,634,000)
Repurchase of common stock	(200,000,000)	(443,000)
Proceeds from issuance of common stock	27,187,000	8,477,000	538,000
Proceeds from (payments on) securitization facility, net	18,000,000	136,000,000	(74,000,000)
Deferred financing costs paid	(3,776,000)	(7,839,000)	(1,067,000)
Principal payments on notes payable	(30,414,000)	(338,965,000)	(24,634,000)
Proceeds from notes payable	250,000,000	300,000,000
Principal payments on revolver	(480,000,000)
Borrowings from revolver	455,000,000	125,000,000
Borrowings on swing line of credit, net	(1,874,000)
Other	(1,490,000)	(179,000)	(17,000)
Net cash provided by (used in) financing activities	61,988,000	236,221,000	(86,544,000)
Effect of foreign currency exchange rates on cash	10,600,000	1,726,000	(1,892,000)
Net (decrease) increase in cash	(1,510,000)	170,355,000	30,103,000
Cash and cash equivalents at beginning of year	285,159,000	114,804,000	84,701,000
Cash and cash equivalents at end of year	283,649,000	285,159,000	114,804,000
Supplemental cash flow information
Cash paid for interest	14,760,000	14,961,000	21,409,000
Cash paid for income taxes	38,169,000	49,205,000	45,998,000
Adoption of new accounting guidance related to asset securitization facility			$ 218,000,000