Condensed Consolidated Statement of Convertible Preferred Stock and Stockholders' Equity - USD ($) $ in Thousands	Total	Series A convertible preferred stock:	Common stock and additional paid-in-capital:	Treasury stock:	Accumulated other comprehensive income (loss):	Accumulated deficit:
Beginning balance at Dec. 31, 2019	$ 701,666		$ 3,457,381	$ (150,000)	$ 1,180	$ (2,606,895)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for equity awards, net of tax withholdings			3,731
Shares withheld for taxes			(8,039)
Issuance of common stock related to employee stock purchase plan			12,300
Shares repurchased			0
Shares retired			70,000	(70,000)
Accretion of series A convertible preferred stock			0
Dividends on series A convertible preferred stock			0
Stock-based compensation			75,152
Unrealized gain (loss) on investments					5,131
Net loss	(129,581)					(129,581)
Ending balance at Jun. 30, 2020	660,360		3,470,525	(80,000)	6,311	(2,736,476)
Beginning balance at Dec. 31, 2019		$ 0
Increase (Decrease) in Temporary Equity [Roll Forward]
Series A convertible preferred stock issuance costs		0
Accretion of series A convertible preferred stock	0	0
Dividend on series A convertible preferred stock	0	0
Ending balance at Jun. 30, 2020		0
Beginning balance at Mar. 31, 2020	653,608		3,488,478	(150,000)	(1,669)	(2,683,201)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for equity awards, net of tax withholdings			2,383
Shares withheld for taxes			(640)
Issuance of common stock related to employee stock purchase plan			12,300
Shares repurchased			0
Shares retired			70,000	(70,000)
Accretion of series A convertible preferred stock			0
Dividends on series A convertible preferred stock			0
Stock-based compensation			38,004
Unrealized gain (loss) on investments					7,980
Net loss	(53,275)					(53,275)
Ending balance at Jun. 30, 2020	660,360		3,470,525	(80,000)	6,311	(2,736,476)
Beginning balance at Mar. 31, 2020		0
Increase (Decrease) in Temporary Equity [Roll Forward]
Series A convertible preferred stock issuance costs		0
Accretion of series A convertible preferred stock		0
Dividend on series A convertible preferred stock		0
Ending balance at Jun. 30, 2020		0
Beginning balance at Dec. 31, 2020	732,905		3,623,268	(80,000)	3,834	(2,814,196)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for equity awards, net of tax withholdings			3,599
Shares withheld for taxes			(9,725)
Issuance of common stock related to employee stock purchase plan			12,335
Shares repurchased	(68,300)		(68,334)
Shares retired			0	0
Accretion of series A convertible preferred stock			(82)
Dividends on series A convertible preferred stock			(9,075)
Stock-based compensation			101,612
Unrealized gain (loss) on investments					(2,415)
Net loss	(115,342)					(115,342)
Ending balance at Jun. 30, 2021	645,479		3,653,598	(80,000)	1,419	(2,929,538)
Beginning balance at Dec. 31, 2020	401,050	401,050
Increase (Decrease) in Temporary Equity [Roll Forward]
Series A convertible preferred stock issuance costs		(82)
Accretion of series A convertible preferred stock	82	82
Dividend on series A convertible preferred stock	9,075	9,075
Ending balance at Jun. 30, 2021	410,124	410,125
Beginning balance at Mar. 31, 2021	715,131		3,657,934	(80,000)	2,040	(2,864,842)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for equity awards, net of tax withholdings			2,502
Shares withheld for taxes			(926)
Issuance of common stock related to employee stock purchase plan			12,335
Shares repurchased	(68,300)		(68,334)
Shares retired			0	0
Accretion of series A convertible preferred stock			0
Dividends on series A convertible preferred stock			(4,563)
Stock-based compensation			54,650
Unrealized gain (loss) on investments					(621)
Net loss	(64,696)					(64,696)
Ending balance at Jun. 30, 2021	645,479		$ 3,653,598	$ (80,000)	$ 1,419	$ (2,929,538)
Beginning balance at Mar. 31, 2021		405,562
Increase (Decrease) in Temporary Equity [Roll Forward]
Series A convertible preferred stock issuance costs		0
Accretion of series A convertible preferred stock		0
Dividend on series A convertible preferred stock		4,563
Ending balance at Jun. 30, 2021	$ 410,124	$ 410,125