CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Class A and B common stock	Additional paid-in capital	Accumulated other comprehensive loss	Accumulated deficit
Beginning balance (in shares) at Dec. 31, 2018		417,048,006
Beginning balance at Dec. 31, 2018	$ 1,120,501	$ 0	$ 2,012,328	$ (6,053)	$ (885,774)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(38,151)				(38,151)
Shares issued in connection with employee stock plans (in shares)		5,582,633
Shares issued in connection with employee stock plans	25,364		25,364
Change in other comprehensive loss	2,629			2,629
Share-based compensation	62,835		62,835
Tax withholding related to vesting of restricted stock units (in shares)		(741,324)
Tax withholding related to vesting of restricted stock units	(50,801)		(50,801)
Issuance of common stock in conjunction with the conversion of senior notes, due 2022 (in shares)		43
Issuance of common stock in conjunction with the conversion of senior notes, due 2022	1		1
Exercise of bond hedges in conjunction with the conversion of senior notes, due 2022 (in shares)		(250,614)
Recovery of common stock in connection with indemnification settlement agreement (in shares)		(14,798)
Recovery of common stock in connection with indemnification settlement agreement	(789)		(789)
Ending balance (in shares) at Mar. 31, 2019		421,623,946
Ending balance at Mar. 31, 2019	1,121,589	$ 0	2,048,938	(3,424)	(923,925)
Beginning balance (in shares) at Dec. 31, 2019		432,796,720
Beginning balance at Dec. 31, 2019	1,715,050	$ 0	2,223,749	1,629	(510,328)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(105,891)				(105,891)
Shares issued in connection with employee stock plans (in shares)		5,222,525
Shares issued in connection with employee stock plans	31,406		31,406
Issuance of common stock in connection with business combination (in shares)		357,017
Issuance of common stock in connection with business combination	14,999		14,999
Change in other comprehensive loss	(5,061)			(5,061)
Share-based compensation	79,562		79,562
Tax withholding related to vesting of restricted stock units (in shares)		(722,606)
Tax withholding related to vesting of restricted stock units	(48,772)		(48,772)
Conversion feature of convertible senior notes, due 2025, net of allocated costs	152,258		152,258
Purchase of bond hedges in conjunction with issuance of convertible senior notes, due 2025	(149,200)		(149,200)
Sale of warrants in conjunction with issuance of convertible senior notes, due 2025	99,500		99,500
Issuance of common stock in conjunction with the conversion of senior notes, due 2022 (in shares)		1,109,980
Issuance of common stock in conjunction with the conversion of senior notes, due 2022	24,094		24,094
Ending balance (in shares) at Mar. 31, 2020		438,763,636
Ending balance at Mar. 31, 2020	$ 1,807,945	$ 0	$ 2,427,596	$ (3,432)	$ (616,219)