Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net income	$ 224,493	$ 232,986
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	250,294	219,234
Stock-based compensation	105,304	92,966
Excess tax benefits from stock-based compensation	(3,080)	(24,851)
Benefit for deferred income taxes	(13,861)	(17,941)
Amortization of debt discount and issuance costs	13,958	13,884
Other non-cash reconciling items, net	8,367	3,271
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	22,477	(40,707)
Prepaid expenses and other current assets	4,014	16,119
Accounts payable and accrued expenses	54,892	26,098
Deferred revenue	6,885	6,908
Other current liabilities	4,670	146
Other non-current assets and liabilities	6,097	18,247
Net cash provided by operating activities	684,510	546,360
Cash flows from investing activities:
Cash paid for acquired businesses, net of cash acquired	(2,936)	(122,445)
Purchases of property and equipment	(134,874)	(262,404)
Capitalization of internal-use software development costs	(105,477)	(103,742)
Purchases of short- and long-term marketable securities	(614,808)	(584,189)
Proceeds from sales of short- and long-term marketable securities	57,900	2,008
Proceeds from maturities of short- and long-term marketable securities	498,633	725,117
Other non-current assets and liabilities	(3,145)	(3,037)
Net cash used in investing activities	(304,707)	(348,692)
Cash flows from financing activities:
Proceeds related to the issuance of common stock under stock plans	42,339	54,288
Excess tax benefits from stock-based compensation	3,080	24,851
Employee taxes paid related to net share settlement of stock-based awards	(38,560)	(47,171)
Repurchases of common stock	(294,867)	(202,426)
Other non-current assets and liabilities	0	(2,050)
Net cash used in financing activities	(288,008)	(172,508)
Effects of exchange rate changes on cash and cash equivalents	535	(7,339)
Net increase in cash and cash equivalents	92,330	17,821
Cash and cash equivalents at beginning of period	289,473	238,650
Cash and cash equivalents at end of period	381,803	256,471
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds received in the nine months ended September 30, 2016 and 2015 of $1,582 and $19,285, respectively	64,716	47,045
Non-cash investing activities:
Purchases of property and equipment and capitalization of internal-use software development costs included in accounts payable and accrued expenses	35,176	27,026
Capitalization of stock-based compensation	$ 17,086	$ 13,133