Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 204,358	$ 195,246
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	318,226	272,917
Stock-based compensation	138,815	122,103
Provision for deferred income taxes	12,906	23,134
Amortization of debt discount and issuance costs	27,844	13,989
Restructuring-related software charges	2,818	0
Other non-cash reconciling items, net	9,360	3,655
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(13,611)	(9,423)
Prepaid expenses and other current assets	(2,084)	(36,580)
Accounts payable and accrued expenses	7,921	22,150
Deferred revenue	23,927	1,528
Other current liabilities	2,030	3,651
Other non-current assets and liabilities	(10,338)	(8,828)
Net cash provided by operating activities	722,172	603,542
Cash flows from investing activities:
Cash paid for acquired businesses, net of cash acquired	(79)	(197,201)
Purchases of property and equipment	(143,285)	(185,466)
Capitalization of internal-use software development costs	(145,122)	(122,460)
Purchases of short- and long-term marketable securities	(782,086)	(249,098)
Proceeds from sales of short- and long-term marketable securities	16,308	180,405
Proceeds from maturities of short- and long-term marketable securities	378,708	317,974
Other non-current assets and liabilities	(2,678)	(1,166)
Net cash used in investing activities	(678,234)	(257,012)
Cash flows from financing activities:
Proceeds from the issuance of convertible senior notes	1,132,185	0
Proceeds from the issuance of warrants	119,945	0
Purchase of note hedge related to convertible senior notes	(261,740)	0
Proceeds related to the issuance of common stock under stock plans	52,497	41,740
Employee taxes paid related to net share settlement of stock-based awards	(52,145)	(48,122)
Repurchases of common stock	(625,925)	(306,629)
Other non-current assets and liabilities	(5,085)	(1,096)
Net cash provided by (used in) financing activities	359,732	(314,107)
Effects of exchange rate changes on cash, cash equivalents and restricted cash	(11,528)	12,359
Net increase in cash, and cash equivalents and restricted cash	392,142	44,782
Cash, cash equivalents and restricted cash at beginning of period	314,429	324,626
Cash, cash equivalents and restricted cash at end of period	706,571	369,408
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds received of $17,286 and $5,867 for the nine months ended September 30, 2018 and 2017, respectively	32,485	79,479
Non-cash investing activities:
Purchases of property and equipment and capitalization of internal-use software development costs included in accounts payable and accrued expenses	54,414	29,546
Capitalization of stock-based compensation	$ 25,676	$ 21,602