Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect of Accounting Change [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] Cumulative Effect of Accounting Change [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] Cumulative Effect of Accounting Change [Member]
Balance at Dec. 31, 2020	$ 761,759	$ (96,792)	$ 8	$ 3,609,877	$ (156,953)	$ 3	$ (2,848,129)	$ 60,161
Balance (in shares) at Dec. 31, 2020			79,374
Exercise of options for common stock	4,683			4,683
Exercise of options for common stock, shares			108
Vest of restricted stock units			204
Issuance of common stock under employee stock purchase plan	4,543			4,543
Issuance of common stock under employee stock purchase plan, shares			62
Stock-based compensation	28,508			28,508
Unrealized gains (losses) from available-for-sale securities, net of tax	(6)					(6)
Net loss	(167,250)						(167,250)
Balance at Mar. 31, 2021	535,445		$ 8	3,490,658		(3)	(2,955,218)
Balance (in shares) at Mar. 31, 2021			79,748
Balance at Dec. 31, 2021	928,009		$ 9	4,134,768		(20)	(3,206,748)
Balance (in shares) at Dec. 31, 2021			87,127
Exercise of options for common stock	997			997
Exercise of options for common stock, shares			18
Vest of restricted stock units			289
Issuance of common stock under employee stock purchase plan	3,993			3,993
Issuance of common stock under employee stock purchase plan, shares			62
Stock-based compensation	29,198			29,198
Unrealized gains (losses) from available-for-sale securities, net of tax	(286)					(286)
Net loss	(105,025)						(105,025)
Balance at Mar. 31, 2022	$ 856,886		$ 9	$ 4,168,956		$ (306)	$ (3,311,773)
Balance (in shares) at Mar. 31, 2022			87,496