Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income	$ 232,986	$ 236,841
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	219,234	179,643
Stock-based compensation	92,966	84,800
Excess tax benefits from stock-based compensation	(24,851)	(23,958)
(Benefit) provision for deferred income taxes	(17,941)	10,622
Amortization of debt discount and issuance costs	13,884	10,939
Other non-cash reconciling items, net	3,271	2,535
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(40,707)	(50,213)
Prepaid expenses and other current assets	16,119	(22,346)
Accounts payable and accrued expenses	26,098	36,876
Deferred revenue	6,908	7,688
Other current liabilities	146	(703)
Other non-current assets and liabilities	18,247	(10,195)
Net cash provided by operating activities	546,360	462,529
Cash flows from investing activities:
Cash paid for acquired businesses, net of cash acquired	(122,445)	(386,532)
Purchases of property and equipment	(262,404)	(142,466)
Capitalization of internal-use software development costs	(103,742)	(83,841)
Purchases of short- and long-term marketable securities	(584,189)	(1,068,198)
Proceeds from sales of short- and long-term marketable securities	2,008	354,313
Proceeds from maturities of short- and long-term marketable securities	725,117	277,109
Other non-current assets and liabilities	(3,037)	7,222
Net cash used in investing activities	(348,692)	(1,042,393)
Cash flows from financing activities:
Proceeds from the issuance of convertible senior notes, net of issuance costs	0	678,735
Proceeds from the issuance of warrants related to convertible senior notes	0	77,970
Purchase of note hedge related to convertible senior notes	0	(101,292)
Repayment of acquired debt and capital leases	0	(17,862)
Proceeds related to the issuance of common stock under stock plans	54,288	75,361
Excess tax benefits from stock-based compensation	24,851	23,958
Employee taxes paid related to net share settlement of stock-based awards	(47,171)	(43,205)
Repurchases of common stock	(202,426)	(226,513)
Other non-current assets and liabilities	(2,050)	(1,575)
Net cash (used in) provided by financing activities	(172,508)	465,577
Effects of exchange rate changes on cash and cash equivalents	(7,339)	(5,265)
Net increase (decrease) in cash and cash equivalents	17,821	(119,552)
Cash and cash equivalents at beginning of period	238,650	333,891
Cash and cash equivalents at end of period	256,471	214,339
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds received in the nine months ended September 30, 2015 of $19,285	47,045	117,723
Non-cash investing and financing activities:
Purchases of property and equipment and capitalization of internal-use software development costs included in accounts payable and accrued expenses	27,026	40,131
Capitalization of stock-based compensation	$ 13,133	$ 11,577