Stockholders' Equity - Common Stock and Warrants (Details) $ / shares in Units, $ in Thousands		1 Months Ended			2 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Apr. 13, 2020 USD ($)	Feb. 28, 2021 USD ($) $ / shares shares	Nov. 30, 2020 USD ($) $ / shares shares	Aug. 31, 2020 USD ($) $ / shares shares	Feb. 28, 2021 USD ($) $ / shares shares	Jun. 30, 2021 $ / shares shares	Mar. 31, 2021 shares	Jun. 30, 2021 USD ($) item $ / shares shares	Jun. 30, 2020 USD ($)	Dec. 31, 2020 $ / shares shares	Dec. 31, 2017 shares
Stockholders' equity
Preferred stock, Shares authorized						5,000,000.0		5,000,000.0
Preferred stock, par value | $ / shares						$ 0.01		$ 0.01
Net proceeds from shares of common stock sold | $			$ 927,300	$ 344,400				$ 3,587,825	$ (269)
Common Stock Shares, Outstanding						570,922,157		570,922,157		458,051,401
Common Stock, Shares, Issued						586,848,225		586,848,225		473,977,469
Common stock, par value (in dollars per share) | $ / shares						$ 0.01		$ 0.01		$ 0.01
Number of votes per share | item								1
Common stock shares issued			43,700,000	35,276,250
Share price (in dollars per share) | $ / shares			$ 22.25	$ 10.25
Number of warrants exercised (in shares)							16,489,014
Proceeds from exercise of warrants, net of transaction costs | $								$ 15,450
Series A Junior Participating Cumulative Preferred Stock
Stockholders' equity
Preferred stock, par value | $ / shares						$ 0.01		$ 0.01
Common Stock Shares, Outstanding						0		0		0
SK Holdings Co LTD
Stockholders' equity
Net proceeds from shares of common stock sold | $		$ 1,600,000
Common stock shares issued		54,966,188
Per share price of shares of common stock | $ / shares		$ 29.2893			$ 29.2893
At Market Issuance Sales Agreement
Stockholders' equity
Authorized amount | $	$ 75,000
Public Offerings
Stockholders' equity
Net proceeds from shares of common stock sold | $					$ 1,800,000
Common stock shares issued					32,200,000
Share price (in dollars per share) | $ / shares		$ 65.00			$ 65.00
Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017
Stockholders' equity
Number of warrants exercised (in shares)						4,745,905
Number of warrants were vested and exercisable								68,380,913		68,380,913
Maximum | Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017
Stockholders' equity
Class of Warrant or Right Issued											110,573,392