CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities
Net income (loss)	$ (241,944)	$ (1,200,921)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	20,231	12,203
Share-based compensation	143,169	1,135,293
Other	3,811	(2,713)
Changes in assets and liabilities:
Accounts receivable	103,544	19,615
Prepaid expenses and other assets	(7,180)	(6,174)
Operating lease right-of-use assets	21,456	14,040
Accounts payable	9,780	7,189
Accrued expenses and other liabilities	(7,743)	15,310
Operating lease liabilities	(24,357)	(10,217)
Net cash provided by (used in) operating activities	20,767	(16,375)
Investing activities
Purchases of property and equipment and intangible assets	(11,325)	(11,914)
Purchases of marketable securities	(308,612)	(159,315)
Sales of marketable securities	113,184	60,239
Maturities of marketable securities	422,266	166,288
Other investing activities	316	0
Net cash provided by investing activities	215,829	55,298
Financing activities
Proceeds from initial public offering, net of underwriters' discounts and commissions	0	1,573,200
Proceeds from exercise of stock options, net	32,749	702
Shares repurchased for tax withholdings on release of restricted stock units	(56,887)	(302,675)
Payment of deferred offering costs and other financing activities	0	(10,103)
Net cash provided by (used in) financing activities	(24,138)	1,261,124
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(150)	(17)
Net increase in cash, cash equivalents, and restricted cash	212,308	1,300,030
Cash, cash equivalents, and restricted cash, beginning of period	677,743	135,290
Cash, cash equivalents, and restricted cash, end of period	890,051	1,435,320
Supplemental cash flow information
Accrued property and equipment	4,453	4,618
Operating lease right-of-use assets obtained in exchange for operating lease liabilities	$ 4,121	$ 23,381