Restatement of Previously Issued Consolidated Financial Statements - Consolidated Statements of Stockholders' Equity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Increase (Decrease) in Stockholders' Equity
Balance	$ 586,265	$ 234,560	$ 104,392	$ 129,904	$ (19,225)	$ (15,795)	$ (7,075)	$ (3,588)	$ 70,229
Balance (in shares)				318,637,560
Balance	$ 1,466,919	586,265	234,560	$ 104,392	$ 129,904	(19,225)	(15,795)	(7,075)	(3,588)
Balance (in shares)	473,977,469				318,637,560
Common Stock
Increase (Decrease) in Stockholders' Equity
Balance	$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342	$ 2,291
Balance (in shares)	406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661	229,073,517
Balance	$ 4,740	$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342
Balance (in shares)	473,977,469	406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661
Additional Paid-in-Capital
Increase (Decrease) in Stockholders' Equity
Balance	$ 2,083,169	$ 1,658,438	$ 1,519,094	$ 1,506,953	$ 1,340,781	$ 1,325,381	$ 1,316,815	$ 1,289,636	$ 1,250,899
Balance	3,446,650	2,083,169	1,658,438	1,519,094	1,506,953	1,340,781	1,325,381	1,316,815	1,289,636
Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity
Balance	1,846	1,159	1,052	1,288	929	1,460	1,374	1,584	2,194
Balance	2,451	1,846	1,159	1,052	1,288	929	1,460	1,374	1,584
Treasury Stock
Increase (Decrease) in Stockholders' Equity
Balance	$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)	$ (3,102)
Balance (in shares)	15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663	587,151
Balance	$ (40,434)	$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)
Balance (in shares)	15,926,068	15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance	$ (1,462,377)	$ (1,397,160)	$ (1,387,752)	$ (1,350,307)	$ (1,332,259)	$ (1,314,425)	$ (1,297,072)	$ (1,266,513)	$ (1,182,053)
Balance	(1,946,488)	(1,462,377)	(1,397,160)	(1,387,752)	(1,350,307)	(1,332,259)	(1,314,425)	(1,297,072)	(1,266,513)
As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	617,444	239,965	109,120	134,679	(14,406)	(10,655)	(1,180)	2,713	73,646
Balance		617,444	239,965	109,120	134,679	(14,406)	(10,655)	(1,180)	2,713
As previously Reported | Common Stock
Increase (Decrease) in Stockholders' Equity
Balance	$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342	$ 2,291
Balance (in shares)	406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661	229,073,517
Balance		$ 4,061	$ 3,482	$ 3,222	$ 3,186	$ 2,540	$ 2,470	$ 2,445	$ 2,342
Balance (in shares)		406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235	234,160,661
As previously Reported | Additional Paid-in-Capital
Increase (Decrease) in Stockholders' Equity
Balance	$ 2,083,199	$ 1,658,532	$ 1,519,257	$ 1,507,116	$ 1,340,859	$ 1,325,459	$ 1,316,893	$ 1,289,714	$ 1,250,899
Balance		2,083,199	1,658,532	1,519,257	1,507,116	1,340,859	1,325,459	1,316,893	1,289,714
As previously Reported | Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity
Balance	1,958	1,271	1,164	1,400	929	1,460	1,374	1,584	2,194
Balance		1,958	1,271	1,164	1,400	929	1,460	1,374	1,584
As previously Reported | Treasury Stock
Increase (Decrease) in Stockholders' Equity
Balance	$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)	$ (3,102)
Balance (in shares)	15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663	587,151
Balance		$ (40,434)	$ (31,359)	$ (31,224)	$ (31,216)	$ (31,216)	$ (30,681)	$ (30,637)	$ (30,637)
Balance (in shares)		15,926,068	15,292,591	15,261,007	15,259,045	15,259,045	15,020,437	15,002,663	15,002,663
As previously Reported | Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance	$ (1,431,340)	$ (1,391,961)	$ (1,383,299)	$ (1,345,807)	$ (1,327,518)	$ (1,309,363)	$ (1,291,255)	$ (1,260,290)	$ (1,178,636)
Balance		(1,431,340)	(1,391,961)	(1,383,299)	(1,345,807)	(1,327,518)	(1,309,363)	(1,291,255)	(1,260,290)
Restatement Adjustments
Increase (Decrease) in Stockholders' Equity
Balance	(31,179)	(5,405)	(4,728)	(4,775)	(4,819)	(5,140)	(5,895)	(6,301)	(3,417)
Balance		(31,179)	(5,405)	(4,728)	(4,775)	(4,819)	(5,140)	(5,895)	(6,301)
Restatement Adjustments | Additional Paid-in-Capital
Increase (Decrease) in Stockholders' Equity
Balance	(30)	(94)	(163)	(163)	(78)	(78)	(78)	(78)
Balance		(30)	(94)	(163)	(163)	(78)	(78)	(78)	(78)
Restatement Adjustments | Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity
Balance	(112)	(112)	(112)	(112)
Balance		(112)	(112)	(112)	(112)
Restatement Adjustments | Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance	$ (31,037)	(5,199)	(4,453)	(4,500)	(4,741)	(5,062)	(5,817)	(6,223)	(3,417)
Balance		$ (31,037)	$ (5,199)	$ (4,453)	$ (4,500)	$ (4,741)	$ (5,062)	$ (5,817)	$ (6,223)