Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net income	$ 180,675	$ 153,132	$ 116,391
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	65,955	60,826	64,186
Deferred income tax benefit	(3,021)	(26,641)	(28,038)
Provision for bad debts	404	1,757	1,610
Stock-based compensation expense	23,088	19,019	13,212
Excess tax benefits from stock options	(10,046)	(11,753)	(13,168)
Other	180	19	108
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	(8,086)	(11,149)	(6,434)
Other receivables and current assets	(16,926)	(61,467)	10,166
Other long-term assets	(1,390)	(60,365)	1,340
Accounts payable, accrued expenses and current liabilities	18,222	16,542	(7,016)
Accrued income taxes	9,668	10,608	19,929
Deferred revenue	49,973	28,817	(606)
Other long-term liabilities	(1,035)	47,539	2,009
Net cash provided by operating activities	307,661	166,884	173,689
Cash flows from investing activities:
Apache acquisition, net of cash acquired	(269,486)	0	0
Capital expenditures	(22,063)	(14,260)	(8,323)
Purchases of short-term investments	(351)	(1,075)	(9,899)
Maturities of short-term investments	257	8,687	7,491
Net cash used in investing activities	(291,643)	(6,648)	(10,731)
Cash flows from financing activities:
Principal payments on long-term debt	(31,889)	(65,630)	(53,924)
Principal payments on capital leases	(87)	(283)	(306)
Purchase of treasury stock	(12,704)	0	(39,904)
Proceeds from issuance of common stock under Employee Stock Purchase Plan	2,167	1,592	1,515
Proceeds from exercise of stock options	22,791	22,929	15,361
Excess tax benefits from stock options	10,046	11,753	13,168
Net cash used in financing activities	(9,676)	(29,639)	(64,090)
Effect of exchange rate fluctuations	(6,993)	6,004	8,834
Net (decrease) increase in cash and cash equivalents	(651)	136,601	107,702
Cash and cash equivalents, beginning of year	472,479	335,878	228,176
Cash and cash equivalents, end of year	471,828	472,479	335,878
Supplemental disclosures of cash flow information:
Income taxes paid	64,731	131,861	58,859
Interest paid	1,858	2,980	8,642
Capital lease obligations incurred	$ 0	$ 0	$ 96