Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 71,487	$ 43,227
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	42,375	45,634
Stock-based compensation expense	22,931	20,924
Provision for doubtful accounts	320	370
Excess tax benefits from stock-based compensation	(4,119)	(13,414)
Gain on investments and disposal of property and equipment, net	(71)	(97)
Loss on divestiture of a business, net	(1,188)	0
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	(28,355)	(1,416)
Prepaid expenses and other current assets	(14,035)	4,309
Accounts payable, accrued expenses and other current liabilities	7,838	(5,798)
Deferred revenue	8,225	1,474
Accrued restructuring	(111)	(2,144)
Other non-current assets and liabilities	(2,257)	(566)
Net cash provided by operating activities	103,040	92,503
Cash flows from investing activities:
Cash paid for acquired businesses, net of cash recevied	0	(291,638)
Purchases of property and equipment	(46,478)	(30,433)
Capitalization of internal-use software costs	(16,998)	(12,911)
Purchases of short- and long-term marketable securities	(145,350)	(280,649)
Proceeds from sales of short- and long-term marketable securities	55,509	28,000
Proceeds from maturities of short- and long-term marketable securities	66,171	89,414
Proceeds from the sale of property and equipment	260	10
Net cash used in investing activities	(86,886)	(498,207)
Cash flows from financing activities:
Proceeds from the issuance of common stock under stock option plans	3,195	7,078
Excess tax benefits from stock-based compensation	4,119	13,414
Employee taxes paid related to net share settlement of equity awards	(17,315)	(21,655)
Repurchases of common stock	(40,278)	(7,913)
Net cash used in financing activities	(50,279)	(9,076)
Effects of exchange rate changes on cash and cash equivalents	(2,589)	307
Net decrease in cash and cash equivalents	(36,714)	(414,473)
Cash and cash equivalents at beginning of period	201,989	559,197
Cash and cash equivalents at end of period	165,275	144,724
Supplemental disclosure of cash flow information:
Cash paid for income taxes	16,097	11,486
Non-cash financing and investing activities:
Capitalization of stock-based compensation, net of impairments	$ 2,938	$ 2,298