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	$ 200,904	$ 171,220	$ 145,913
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	167,878	143,242	122,494
Amortization of deferred financing costs	0	507	840
Share-based compensation expense	61,305	76,468	58,797
Provision for deferred income taxes, net	53,628	62,462	81,706
Provision for doubtful accounts	2,066	1,546	6,727
Excess tax benefits from stock-based compensation	(13,123)	(28,973)	(2,236)
Non-cash portion of loss on early extinguishment of debt	0	299	0
Non-cash portion of restructuring charge	412	0	0
Loss (gain) on investments and disposal of property and equipment, net	597	(428)	(391)
Gain on divesture of certain assets	0	0	(1,062)
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(37,837)	(23,563)	(1,159)
Prepaid expenses and other current assets	(7,014)	(12,089)	(5,020)
Accounts payable, accrued expenses and other current liabilities	15,184	20,529	10,255
Deferred revenue	(3,721)	(9,454)	5,871
Accrued restructuring	3,572	(617)	(1,067)
Other non-current assets and liabilities	8,704	1,306	2,744
Net cash provided by operating activities	452,555	402,455	424,412
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(550)	(12,668)	(5,779)
Purchases of property and equipment	(140,218)	(159,276)	(80,918)
Capitalization of internal-use software costs	(42,644)	(32,769)	(27,229)
Purchases of short- and long-term marketable securities	(880,110)	(1,146,493)	(790,351)
Proceeds from sales and redemptions of short- and long-term marketable securities	701,313	691,227	403,559
Proceeds from maturities of short- and long-term marketable securities	532,910	324,606	141,544
Increase in other investments	0	(500)	0
Proceeds from the sale of property and equipment	150	176	93
Proceeds from divesture of certain assets	0	0	1,350
Decrease in restricted investments held for security deposits	272	338	233
Net cash provided by (used in) investing activities	171,123	(335,359)	(357,498)
Cash flows from financing activities:
Proceeds from the issuance of common stock under stock option and employee stock purchase plans	25,252	45,776	21,724
Excess tax benefits from stock-based compensation	13,123	28,973	2,236
Employee taxes paid related to net share settlement of equity awards	(8,393)	0	0
Repurchases of common stock	(324,070)	(92,425)	(66,497)
Net cash used in financing activities	(294,088)	(17,676)	(42,537)
Effects of exchange rate changes on cash and cash equivalents	(2,259)	1,141	854
Net increase in cash and cash equivalents	327,331	50,561	25,231
Cash and cash equivalents at beginning of year	231,866	181,305	156,074
Cash and cash equivalents at end of year	559,197	231,866	181,305
Supplemental disclosure of cash flow information:
Cash paid for interest	0	1,258	1,998
Cash paid for income taxes	45,578	26,200	20,989
Non-cash financing and investing activities:
Capitalization of stock-based compensation, net of impairments	7,473	7,818	6,280
Common stock issued upon conversion of 1% convertible senior notes	0	199,755	100
Common stock returned upon settlement of escrow claims related to prior business acquisitions	$ 0	$ (430)	$ (427)