CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net income	$ 203,483	$ 180,675	$ 153,132
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	85,422	65,955	60,826
Deferred income tax benefit	(18,896)	(3,021)	(26,641)
Provision for bad debts	938	404	1,757
Stock-based compensation expense	32,415	23,088	19,019
Excess tax benefits from stock options	(13,888)	(10,046)	(11,753)
Other	69	180	19
Changes in operating assets and liabilities:
Accounts receivable	(12,401)	(8,086)	(11,149)
Other receivables and current assets	(50,485)	(16,926)	(61,467)
Other long-term assets	5,027	(1,390)	(60,365)
Accounts payable, accrued expenses and current liabilities	9,548	18,222	16,542
Accrued income taxes	14,616	9,668	10,608
Deferred revenue	47,748	49,973	28,817
Other long-term liabilities	(5,181)	(1,035)	47,539
Net cash provided by operating activities	298,415	307,661	166,884
Cash flows from investing activities:
Acquisitions, net of cash acquired	(45,075)	(269,486)	0
Capital expenditures	(23,977)	(22,063)	(14,260)
Purchases of short-term investments	(228)	(351)	(1,075)
Maturities of short-term investments	324	257	8,687
Net cash used in investing activities	(68,956)	(291,643)	(6,648)
Cash flows from financing activities:
Principal payments on long-term debt	(74,408)	(31,889)	(65,630)
Principal payments on capital leases	(14)	(87)	(283)
Purchase of treasury stock	(95,477)	(12,704)	0
Contingent consideration payments	(3,241)	0	0
Proceeds from issuance of common stock under Employee Stock Purchase Plan	2,446	2,167	1,592
Proceeds from exercise of stock options	31,960	22,791	22,929
Excess tax benefits from stock options	13,888	10,046	11,753
Net cash used in financing activities	(124,846)	(9,676)	(29,639)
Effect of exchange rate fluctuations on cash and cash equivalents	262	(6,993)	6,004
Net increase (decrease) in cash and cash equivalents	104,875	(651)	136,601
Cash and cash equivalents, beginning of period	471,828	472,479	335,878
Cash and cash equivalents, end of period	576,703	471,828	472,479
Supplemental disclosures of cash flow information:
Income taxes paid	103,196	64,731	131,861
Interest paid	$ 1,970	$ 1,858	$ 2,980