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	$ 203,989	$ 200,904	$ 171,220
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	204,163	167,878	143,242
Amortization of deferred financing costs	0	0	507
Stock-based compensation expense	90,585	61,305	76,468
Provision for deferred income taxes, net	(5,819)	53,628	62,462
Provision for doubtful accounts	(316)	2,066	1,546
Excess tax benefits from stock-based compensation	(23,015)	(13,123)	(28,973)
Non-cash portion of loss on early extinguishment of debt	0	0	299
Non-cash portion of restructuring charge	0	412	0
Loss (gain) on investments and disposal of property and equipment, net	3	597	(428)
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(2,108)	(37,837)	(23,563)
Prepaid expenses and other current assets	6,066	(7,014)	(12,089)
Accounts payable, accrued expenses and other current liabilities	59,653	15,184	20,529
Deferred revenue	4,552	(3,721)	(9,454)
Accrued restructuring	(3,278)	3,572	(617)
Other non-current assets and liabilities	(4,070)	8,704	1,306
Net cash provided by operating activities	530,405	452,555	402,455
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(336,680)	(550)	(12,668)
Purchases of property and equipment	(165,642)	(140,218)	(159,276)
Capitalization of internal-use software costs	(54,204)	(42,644)	(32,769)
Purchases of short- and long-term marketable securities	(752,342)	(880,110)	(1,146,493)
Proceeds from sales and redemptions of short- and long-term marketable securities	214,277	701,313	691,227
Proceeds from maturities of short- and long-term marketable securities	315,788	532,910	324,606
Increase in other investments	(250)	0	(500)
Proceeds from sale of property and equipment	12	150	176
Decrease in restricted investments held for security deposits	0	272	338
Net cash (used in) provided by investing activities	(779,041)	171,123	(335,359)
Cash flows from financing activities:
Proceeds from the issuance of common stock under stock option and employee stock purchase plans	44,660	25,252	45,776
Excess tax benefits from stock-based compensation	23,015	13,123	28,973
Employee taxes paid related to net share settlement of equity awards	(34,690)	(8,393)	0
Repurchases of common stock	(141,468)	(324,070)	(92,425)
Net cash used in financing activities	(108,483)	(294,088)	(17,676)
Effects of exchange rate changes on cash and cash equivalents	(89)	(2,259)	1,141
Net (decrease) increase in cash and cash equivalents	(357,208)	327,331	50,561
Cash and cash equivalents at beginning of year	559,197	231,866	181,305
Cash and cash equivalents at end of year	201,989	559,197	231,866
Supplemental disclosure of cash flow information:
Cash paid for interest	0	0	1,258
Cash paid for income taxes	94,833	45,578	26,200
Non-cash financing and investing activities:
Capitalization of stock-based compensation, net of impairments	9,276	7,473	7,818
Common stock issued upon conversion of 1% convertible senior notes	0	0	199,755
Common stock returned upon settlement of escrow claims related to prior business acquisitions	$ 0	$ 0	$ (430)