Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income	$ 213,138	$ 135,697
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	134,455	149,203
Stock-based compensation	72,211	69,180
Excess tax benefits from stock-based compensation	(18,152)	(17,589)
Provision for deferred income taxes	0	826
Provision for doubtful accounts	889	(61)
Gain from disposal of property and equipment	(15)	(62)
Gain from divestiture of a business	(1,188)	0
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	(51,321)	(21,587)
Prepaid expenses and other current assets	(9,266)	10,010
Accounts payable and accrued expenses	43,730	49,149
Deferred revenue	10,991	5,542
Other current liabilities	32	(2,897)
Other non-current assets and liabilities	(3,328)	(104)
Net cash provided by operating activities	392,176	377,307
Cash flows from investing activities:
Cash paid for acquired businesses, net of cash acquired	(27,420)	(306,030)
Purchases of property and equipment	(142,567)	(119,116)
Capitalization of internal-use software development costs	(55,171)	(39,921)
Purchases of short- and long-term marketable securities	(403,556)	(554,303)
Proceeds from sales of short- and long-term marketable securities	79,207	135,993
Proceeds from maturities of short- and long-term marketable securities	265,495	214,159
Proceeds from the sale of property and equipment	761	12
Other non-currents assets and liabilities	(3,320)	979
Net cash used in investing activities	(286,571)	(668,227)
Cash flows from financing activities:
Proceeds related to the issuance of common stock under stock plans	54,418	33,760
Excess tax benefits from stock-based compensation	18,152	17,589
Employee taxes paid related to net share settlement of stock-based awards	(28,559)	(26,566)
Repurchases of common stock	(112,408)	(111,649)
Net cash used in financing activities	(68,397)	(86,866)
Effects of exchange rate changes on cash and cash equivalents	(4,182)	1,239
Net increase (decrease) in cash and cash equivalents	33,026	(376,547)
Cash and cash equivalents at beginning of period	201,989	559,197
Cash and cash equivalents at end of period	235,015	182,650
Supplemental disclosure of cash flow information:
Cash paid for income taxes	44,191	51,822
Non-cash financing and investing activities:
Purchases of property and equipment included in accrued expenses	12,630	12,939
Capitalization of stock-based compensation, net of impairments	9,252	6,694
Convertible note receivable received for divestiture of a business	$ 18,882	$ 0