CONSOLIDATED BALANCE SHEETS (Parenthetical) - 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
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
Common stock in treasury, shares	15,926,068				15,259,045
Series C Redeemable Convertible Preferred Stock
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 Convertible Preferred Stock
Redeemable convertible Preferred Stock, par value (in dollars per share)	$ 0.01				$ 0.01
Redeemable convertible Preferred Stock, shares authorized	35,000				35,000
Redeemable convertible Preferred Stock, shares issued	0				500
Redeemable convertible Preferred Stock, shares outstanding	0				500