Consolidated Statements of Stockholders' Equity/Deficit-Unaudited - USD ($) shares in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Gain (Loss)	Treasury Stock
Balance, shares at Dec. 31, 2020		142,289
Balance, value at Dec. 31, 2020	$ 156,371,000	$ 142,000	$ 1,561,096,000	$ (1,400,018,000)	$ (6,000)	$ (4,843,000)
Stock-based compensation	2,851,000	$ 0	2,851,000	0	0	0
Issuance of common stock under Equity Incentive Plans, shares		2,000
Issuance of common stock under Equity Incentive Plans, value	(16,399,000)	$ (2,000)	(16,397,000)	0	0	0
Repurchase of common stock	(2,675,000)	0	0	0	0	(2,675,000)
Net loss		0	0	(20,958,000)	0	0
Unrealized gain on investments	11,000	$ 0	0	0	11,000	0
Balance, shares at Mar. 31, 2021		145,552
Balance, value at Mar. 31, 2021	152,547,000	$ 145,000	1,580,891,000	(1,420,976,000)	5,000	(7,518,000)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures		1,263
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	548,000	$ 1,000	547,000	0	0	0
Balance, shares at Dec. 31, 2020		142,289
Balance, value at Dec. 31, 2020	156,371,000	$ 142,000	1,561,096,000	(1,400,018,000)	(6,000)	(4,843,000)
Net loss	(39,025,000)
Unrealized gain on investments	1,000
Balance, shares at Jun. 30, 2021		145,640
Balance, value at Jun. 30, 2021	137,233,000	$ 146,000	1,583,653,000	(1,439,043,000)	(5,000)	(7,518,000)
Stock Issued During Period, Value, Treasury Stock Reissued	0
Balance, shares at Mar. 31, 2021		145,552
Balance, value at Mar. 31, 2021	152,547,000	$ 145,000	1,580,891,000	(1,420,976,000)	5,000	(7,518,000)
Stock-based compensation	2,786,000	0	2,786,000	0	0	0
Payments of Stock Issuance Costs	(31,000)	0	(31,000)	0	0	0
Net loss	(18,067,000)	0	0	(18,067,000)	0	0
Unrealized gain on investments	(10,000)	$ 0	0	0	(10,000)	0
Balance, shares at Jun. 30, 2021		145,640
Balance, value at Jun. 30, 2021	137,233,000	$ 146,000	1,583,653,000	(1,439,043,000)	(5,000)	(7,518,000)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures		88
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	$ 8,000	$ 1,000	7,000	0	0	0
Balance, shares at Dec. 31, 2021	150,082	150,082
Balance, value at Dec. 31, 2021	$ 113,595,000	$ 150,000	1,608,749,000	(1,487,776,000)	(10,000)	(7,518,000)
Stock-based compensation	2,772,000	$ 0	2,772,000	0	0	0
Issuance of common stock under Equity Incentive Plans, shares		0
Issuance of common stock under Equity Incentive Plans, value	(864,000)	$ 0	0	0	0	864,000
Net loss	(23,476,000)	0	0	(23,476,000)	0	0
Unrealized gain on investments	(27,000)	$ 0	0	0	(27,000)	0
Balance, shares at Mar. 31, 2022		150,082
Balance, value at Mar. 31, 2022	92,698,000	$ 150,000	1,605,898,000	(1,511,252,000)	(37,000)	(2,061,000)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures		0
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	698,000	$ 0	698,000	0	0	0
Stock Issued During Period, Value, Treasury Stock Reissued	$ 0	$ 0	(6,321,000)	0	0	(6,321,000)
Stock Issued During Period, Shares, Treasury Stock Reissued		0
Balance, shares at Dec. 31, 2021	150,082	150,082
Balance, value at Dec. 31, 2021	$ 113,595,000	$ 150,000	1,608,749,000	(1,487,776,000)	(10,000)	(7,518,000)
Net loss	(48,063,000)
Unrealized gain on investments	$ (140,000)
Balance, shares at Jun. 30, 2022	150,114	150,114
Balance, value at Jun. 30, 2022	$ 70,830,000	$ 150,000	1,608,730,000	(1,535,839,000)	(150,000)	(2,061,000)
Stock Issued During Period, Value, Treasury Stock Reissued	(6,321)
Balance, shares at Mar. 31, 2022		150,082
Balance, value at Mar. 31, 2022	92,698,000	$ 150,000	1,605,898,000	(1,511,252,000)	(37,000)	(2,061,000)
Stock-based compensation	2,832,000	$ 0	2,832,000	0	0	0
Issuance of common stock under Equity Incentive Plans, shares		32
Issuance of common stock under Equity Incentive Plans, value	0	$ 0	0	0	0	0
Net loss	(24,587,000)	0	0	(24,587,000)	0	0
Unrealized gain on investments	$ (113,000)	$ 0	0	0	(113,000)	0
Balance, shares at Jun. 30, 2022	150,114	150,114
Balance, value at Jun. 30, 2022	$ 70,830,000	$ 150,000	$ 1,608,730,000	$ (1,535,839,000)	$ (150,000)	$ (2,061,000)