Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 221,045	$ 96,775
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	214,270	210,393
Stock-based compensation	93,447	92,183
Provision (benefit) for deferred income taxes	24,608	(12,116)
Amortization of debt discount and issuance costs	19,628	13,759
Restructuring-related software charges	0	2,818
Other non-cash reconciling items, net	1,180	8,015
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(38,127)	(16,889)
Prepaid expenses and other current assets	(23,287)	8,578
Accounts payable and accrued expenses	(52,789)	(27,091)
Deferred revenue	27,973	29,552
Other current liabilities	(18,739)	5,655
Other non-current assets and liabilities	9,570	59
Net cash provided by operating activities	478,779	411,691
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	(158,158)	(98,300)
Capitalization of internal-use software development costs	(117,620)	(103,409)
Purchases of short- and long-term marketable securities	(391,758)	(467,886)
Proceeds from sales of short- and long-term marketable securities	268	16,196
Proceeds from maturities of short- and long-term marketable securities	649,262	124,370
Other non-current assets and liabilities	2,237	(479)
Net cash used in investing activities	(173,186)	(529,587)
Cash flows from financing activities:
Proceeds from the issuance of convertible senior notes	0	1,132,622
Proceeds from the issuance of warrants	0	119,945
Purchase of note hedge related to convertible senior notes	0	(261,740)
Repayment of convertible senior notes	(690,000)	0
Proceeds related to the issuance of common stock under stock plans	28,772	34,103
Employee taxes paid related to net share settlement of stock-based awards	(49,956)	(41,308)
Repurchases of common stock	(116,247)	(185,512)
Other non-current assets and liabilities	(1,558)	(4,844)
Net cash (used in) provided by financing activities	(828,989)	793,266
Effects of exchange rate changes on cash, cash equivalents and restricted cash	2,678	(11,460)
Net (decrease) increase in cash, cash equivalents and restricted cash	(520,718)	663,910
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	516,269	978,339
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds received of $2,216 and $8,656 for the six months ended June 30, 2019 and 2018, respectively	54,271	28,088
Cash paid for operating lease liabilities	69,317
Non-cash activities:
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	63,709
Purchases of property and equipment and capitalization of internal-use software development costs included in accounts payable and accrued expenses	71,066	34,016
Capitalization of stock-based compensation	$ 18,760	$ 16,891