Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 358,935	$ 204,358
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	324,874	318,226
Stock-based compensation	140,262	138,815
Provision for deferred income taxes	24,581	12,906
Amortization of debt discount and issuance costs	30,761	27,844
Restructuring-related software charges	0	2,818
Other non-cash reconciling items, net	3,778	9,360
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(38,144)	(13,611)
Prepaid expenses and other current assets	(11,663)	(2,084)
Accounts payable and accrued expenses	(29,441)	7,921
Deferred revenue	16,714	23,927
Other current liabilities	(21,850)	2,030
Other non-current assets and liabilities	(22,643)	(10,338)
Net cash provided by operating activities	776,164	722,172
Cash flows from investing activities:
Cash paid for acquired businesses, net of cash acquired	(121,409)	(79)
Cash paid for equity method investment	(36,008)	0
Purchases of property and equipment	(268,766)	(143,285)
Capitalization of internal-use software development costs	(159,645)	(145,122)
Purchases of short- and long-term marketable securities	(1,373,563)	(782,086)
Proceeds from sales of short- and long-term marketable securities	547	16,308
Proceeds from maturities of short- and long-term marketable securities	878,779	378,708
Other non-current assets and liabilities	1,895	(2,678)
Net cash used in investing activities	(1,078,170)	(678,234)
Cash flows from financing activities:
Proceeds from the issuance of convertible senior notes	1,135,629	1,132,185
Proceeds from the issuance of warrants	185,150	119,945
Purchase of note hedge related to convertible senior notes	(312,225)	(261,740)
Repayment of convertible senior notes	(690,000)	0
Proceeds related to the issuance of common stock under stock plans	43,204	52,497
Employee taxes paid related to net share settlement of stock-based awards	(61,116)	(52,145)
Repurchases of common stock	(291,788)	(625,925)
Other non-current assets and liabilities	(1,558)	(5,085)
Net cash provided by financing activities	7,296	359,732
Effects of exchange rate changes on cash, cash equivalents and restricted cash	(2,650)	(11,528)
Net (decrease) increase in cash, cash equivalents and restricted cash	(297,360)	392,142
Cash, cash equivalents and restricted cash at beginning of period	1,036,987	314,429
Cash, cash equivalents and restricted cash at end of period	739,627	706,571
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds received of $2,746 and $17,286 for the nine months ended September 30, 2019 and 2018, respectively	65,896	32,485
Cash paid for operating lease liabilities	107,478
Non-cash activities:
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	87,207
Purchases of property and equipment and capitalization of internal-use software development costs included in accounts payable and accrued expenses	64,982	54,414
Capitalization of stock-based compensation	$ 27,352	$ 25,676