Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Net income	$ 43,227	$ 50,617
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	45,634	41,134
Stock-based compensation expense	20,924	15,712
Provision for doubtful accounts	370	322
Excess tax benefits from stock-based compensation	(13,414)	(9,012)
(Gain) Loss on investments and disposal of property and equipment, net	(97)	117
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(1,416)	7,557
Prepaid expenses and other current assets	4,309	(6,076)
Accounts payable, accrued expenses and other current liabilities	(5,798)	(8,391)
Deferred revenue	1,474	(3,453)
Accrued restructuring	(2,144)	0
Other non-current assets and liabilities	(566)	(16)
Net cash provided by operating activities	92,503	88,511
Cash flows from investing activities:
Cash paid for acquisition of business, net of cash acquired	(291,638)	(175)
Purchases of property and equipment	(30,433)	(35,600)
Capitalization of internal-use software costs	(12,911)	(10,635)
Purchases of short- and long-term marketable securities	(280,649)	(275,615)
Proceeds from sales of short- and long-term marketable securities	28,000	110,034
Proceeds from maturities of short- and long-term marketable securities	89,414	137,233
Proceeds from the sale of property and equipment	10	25
Decrease in restricted investments held for security deposits	0	221
Net cash provided by (used in) investing activities	(498,207)	(74,512)
Cash flows from financing activities:
Proceeds from the issuance of common stock under stock option and employee stock purchase plans	7,078	3,959
Excess tax benefits from stock-based compensation	13,414	9,012
Employee taxes paid related to net share settlement of equity awards	(21,655)	0
Repurchases of common stock	(7,913)	(43,678)
Net cash used in financing activities	(9,076)	(30,707)
Effects of exchange rate changes on cash and cash equivalents	307	2,016
Net decrease in cash and cash equivalents	(414,473)	(14,692)
Cash and cash equivalents at beginning of period	559,197	231,866
Cash and cash equivalents at end of period	144,724	217,174
Supplemental disclosure of cash flow information:
Cash paid for income taxes	11,486	9,482
Non-cash financing and investing activities:
Capitalization of stock-based compensation, net of impairments	$ 2,298	$ 1,824