Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements - Consolidated Balance Sheets (Narrative) (Details) - USD ($) $ / shares in Units, $ 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
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Redeemable convertible Preferred Stock, par value (in dollars per share)						$ 0.01
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Common Stock, Shares Authorized	750,000,000	750,000,000	750,000,000	750,000,000	750,000,000	750,000,000	750,000,000	750,000,000
Common stock, shares issued	473,977,469	406,123,816	348,201,792	322,220,469	318,637,560	253,982,578	246,975,173	244,537,235
Series C Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Redeemable convertible Preferred Stock, par value (in dollars per share)	$ 0.01			$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Redeemable convertible Preferred Stock, shares authorized	10,431			10,431	10,431	10,431	10,431	10,431
Redeemable convertible Preferred Stock, shares issued	0			2,620	2,620	2,620	2,620	2,620
Redeemable convertible Preferred Stock, shares outstanding	0			2,620	2,620	2,620	2,620	2,620
Redeemable convertible Preferred Stock, aggregate involuntary liquidation preference (in dollars)	$ 16,664			$ 16,664	$ 16,664		$ 16,664	$ 16,664
Series E Redeemable Convertible Preferred Stock
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Redeemable convertible Preferred Stock, par value (in dollars per share)					$ 0.01	$ 0.01	$ 0.01	$ 0.01
Redeemable convertible Preferred Stock, shares authorized					35,000,000	35,000	35,000	35,000
Redeemable convertible Preferred Stock, shares issued					500,000	28,269	35,000	35,000
Redeemable convertible Preferred Stock, shares outstanding					500,000	28,269	35,000	35,000
Redeemable convertible Preferred Stock, aggregate involuntary liquidation preference (in dollars)							$ 35,000	$ 35,000