Stockholders' Equity - Common Stock and Warrants (Details) $ / shares in Units, $ in Thousands		1 Months Ended						3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Apr. 13, 2020 USD ($)	Feb. 28, 2021 USD ($) $ / shares shares	Jan. 31, 2021 USD ($) $ / shares shares	Nov. 30, 2020 USD ($) $ / shares shares	Aug. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2020 $ / shares shares	Mar. 31, 2019 USD ($) $ / shares shares	Jun. 30, 2020 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) item $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 shares	Mar. 31, 2020 $ / shares 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	$ 120,400	$ 23,500		$ 23,498	$ (269)	$ 28,265	$ 344,398	$ 38,098	$ 1,271,714	$ 158,343	$ 7,195
Common Stock Shares, Outstanding						303,378,515		458,051,920						458,051,920	303,378,515
Common Stock, Shares, Issued						318,637,560	244,537,235	473,977,469	244,537,235	348,201,792	246,975,173	406,123,816	253,982,578	473,977,469	318,637,560			322,220,469
Common stock, par value (in dollars per share) | $ / shares						$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01	$ 0.01			$ 0.01
Number of votes per share | item														1
Common stock shares issued				43,700,000	35,276,250	46,000,000	10,000,000	4,400,000						79,000,000.0
Share price (in dollars per share) | $ / shares				$ 22.25	$ 10.25	$ 2.75	$ 2.35		$ 2.35						$ 2.75
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	0
At Market Issuance Sales Agreement
Stockholders' equity
Net proceeds from shares of common stock sold | $															$ 14,500	$ 7,000
Common stock shares issued															6,300,000	3,800,000
Authorized amount | $	$ 75,000
Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017
Stockholders' equity
Number of warrants exercised (in shares)														68,380,913	26,188,434
Maximum | Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017
Stockholders' equity
Class of Warrant or Right Issued																	110,573,392
Subsequent event
Stockholders' equity
Common stock shares issued		54,966,188
Subsequent event | SK Holdings Co LTD
Stockholders' equity
Net proceeds from shares of common stock sold | $		$ 1,600,000
Common Stock, Shares, Issued		54,966,188
Common stock shares issued		54,996,188
Per share price of shares of common stock | $ / shares		$ 29.2893
Subsequent event | Public Offerings
Stockholders' equity
Net proceeds from shares of common stock sold | $		$ 1,800,000	$ 1,800,000
Common stock shares issued		32,200,000	32,200,000
Share price (in dollars per share) | $ / shares		$ 65.00	$ 65.00