Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited interim Condensed Consolidated Financial Statements - Condensed 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	Dec. 31, 2017
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)	406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235
Balance	$ 1,466,919	$ 586,265	$ 234,560	$ 104,392	$ 129,904	$ (19,225)	$ (15,795)	$ (7,075)	(3,588)	$ 70,229
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
As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	$ 617,444	$ 239,965	$ 109,120	$ 134,679	$ (14,406)	$ (10,655)	$ (1,180)	$ 134,679	2,713	73,646
Balance		617,444	239,965	109,120	134,679	(14,406)	(10,655)	(1,180)	134,679	2,713
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)	(3,417)
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	$ 2,291
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	229,073,517
Common Stock | As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	$ 4,061	$ 3,482	$ 3,222		$ 2,540	$ 2,470	$ 2,445	$ 3,186	$ 2,342	$ 2,291
Balance (in shares)	406,123,816	348,201,792	322,220,469		253,982,578	246,975,173	244,537,235	318,637,560	234,160,661	229,073,517
Balance		$ 4,061	$ 3,482	$ 3,222		$ 2,540	$ 2,470	$ 2,445	$ 3,186	$ 2,342
Balance (in shares)		406,123,816	348,201,792	322,220,469		253,982,578	246,975,173	244,537,235	318,637,560	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	$ 1,250,899
Additional Paid-in-Capital | As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	2,083,199	1,658,532	1,519,257		1,340,859	1,325,459	1,316,893	1,507,116	1,289,714	1,250,899
Balance		2,083,199	1,658,532	1,519,257		1,340,859	1,325,459	1,316,893	1,507,116	1,289,714
Additional Paid-in-Capital | Restatement Adjustments
Increase (Decrease) in Stockholders' Equity
Balance	(30)	(94)	(163)	(163)	(78)	(78)	(78)	(78)
Balance		(30)	(94)	(163)	(163)	(78)	(78)	(78)	(78)
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	2,194
Accumulated Other Comprehensive Income | As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	1,958	1,271	1,164		929	1,460	1,374	1,400	1,584	2,194
Balance		1,958	1,271	1,164		929	1,460	1,374	1,400	1,584
Accumulated Other Comprehensive Income | Restatement Adjustments
Increase (Decrease) in Stockholders' Equity
Balance	(112)	(112)	(112)	(112)
Balance		(112)	(112)	(112)	(112)
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)	$ (3,102)
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	587,151
Treasury Stock | As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	$ (40,434)	$ (31,359)	$ (31,224)		$ (31,216)	$ (30,681)	$ (30,637)	$ (31,216)	$ (30,637)	$ (3,102)
Balance (in shares)	15,926,068	15,292,591	15,261,007		15,259,045	15,020,437	15,002,663	15,259,045	15,002,663	587,151
Balance		$ (40,434)	$ (31,359)	$ (31,224)		$ (31,216)	$ (30,681)	$ (30,637)	$ (31,216)	$ (30,637)
Balance (in shares)		15,926,068	15,292,591	15,261,007		15,259,045	15,020,437	15,002,663	15,259,045	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)	$ (1,182,053)
Accumulated Deficit | As previously Reported
Increase (Decrease) in Stockholders' Equity
Balance	(1,431,340)	(1,391,961)	(1,383,299)		(1,327,518)	(1,309,363)	(1,291,255)	(1,345,807)	(1,260,290)	(1,178,636)
Balance		(1,431,340)	(1,391,961)	(1,383,299)		(1,327,518)	(1,309,363)	(1,291,255)	(1,345,807)	(1,260,290)
Accumulated Deficit | Restatement Adjustments
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)	$ (3,417)