Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 321,406	$ 333,948	$ 293,487
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	299,563	247,406	184,431
Stock-based compensation	126,677	111,996	95,884
Excess tax benefits from stock-based compensation	(29,301)	(32,238)	(22,801)
Provision (benefit) for deferred income taxes	4,098	(25,880)	27,343
Amortization of debt discount and issuance costs	18,525	15,463	0
Other non-cash reconciling items, net	5,804	2,565	1,176
Changes in operating assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	(56,247)	(58,397)	(67,184)
Prepaid expenses and other current assets	7,137	(60,788)	(3,842)
Accounts payable and accrued expenses	51,624	94,698	40,533
Deferred revenue	3,224	7,725	11,495
Other current liabilities	(345)	(702)	52
Other non-current assets and liabilities	11,986	22,274	3,334
Net cash provided by operating activities	764,151	658,070	563,908
Cash flows from investing activities:
Cash paid for acquisitions, net of cash acquired	(141,147)	(386,532)	(30,657)
Purchases of property and equipment	(311,676)	(207,159)	(187,964)
Capitalization of internal-use software development costs	(133,307)	(111,468)	(72,109)
Purchases of short- and long-term marketable securities	(692,879)	(1,225,409)	(494,885)
Proceeds from sales of short- and long-term marketable securities	2,008	373,730	160,210
Proceeds from maturities of short- and long-term marketable securities	843,931	372,287	314,925
Other non-current assets and liabilities	(2,494)	5,745	(2,628)
Net cash used in by investing activities	(435,564)	(1,178,806)	(313,108)
Cash flows from financing activities:
Proceeds from the issuance of convertible senior notes, net of issuance costs	0	678,735	0
Proceeds from the issuance of warrants related to convertible senior notes	0	77,970	0
Purchase of note hedge related to convertible senior notes	0	(101,292)	0
Repayment of acquired debt and capital leases	0	(17,862)	0
Proceeds related to the issuance of common stock under stock plans	61,791	87,109	63,707
Excess tax benefits from stock-based compensation	29,301	32,238	22,801
Employee taxes paid related to net share settlement of stock-based awards	(54,164)	(50,649)	(41,332)
Repurchases of common stock	(302,606)	(268,647)	(160,419)
Other non-current assets and liabilities	(2,050)	(1,575)	0
Net cash provided by (used in) financing activities	(267,728)	436,027	(115,243)
Effects of exchange rate changes on cash and cash equivalents	(10,036)	(10,532)	(3,655)
Net increase (decrease) in cash and cash equivalents	50,823	(95,241)	131,902
Cash and cash equivalents at beginning of year	238,650	333,891	201,989
Cash and cash equivalents at end of year	289,473	238,650	333,891
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds received in the year ended December 31, 2015 of $19,374	75,033	166,211	63,508
Non-cash financing and investing activities:
Purchases of property and equipment and capitalization of internal-use software development costs included in accounts payable and accrued expenses	19,327	45,868	19,927
Capitalization of stock-based compensation	17,867	15,226	12,325
Convertible note receivable received for divestiture of a business	$ 0	$ 0	$ 18,882