Earnings Per Share - Dilutive Potential Common Shares (Details) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended				6 Months Ended
	Jan. 07, 2021	Jul. 01, 2020	Jul. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jan. 31, 2021	Jan. 01, 2021	May 31, 2020	May 29, 2020	May 18, 2020	Sep. 30, 2019	Mar. 31, 2018	Jul. 20, 2017	Apr. 04, 2017
Earnings Per Share
Number of dilutive potential common stock								138,366,461	204,174,726
Stock options granted								698,500	174,649
Number of warrants exercised (in shares)					16,489,014
Conversion of notes through common stock issuance		16,000,000.0
Interest rate (as a percent)											3.75%
3.75% Convertible Senior Notes
Earnings Per Share
Principal amount				$ 197,278				$ 197,278				$ 212,463	$ 12,500	$ 200,000
Conversion of notes through common stock issuance					3,016,036			3,000,000.0
Convertible senior notes					$ 15,200
Interest rate (as a percent)				3.75%	3.75%			3.75%				3.75%	3.75%	3.75%
7.5% Convertible Senior Note
Earnings Per Share
Interest rate (as a percent)															7.50%
5.5% Convertible Senior Notes
Earnings Per Share
Principal amount	$ 160					$ 33,500								$ 100,000		$ 100,000
Outstanding balance										$ 160
Conversion of notes through common stock issuance	69,808					14,600,000
Debt Instrument, Repurchased Face Amount												$ 66,300
Interest rate (as a percent)	5.50%			5.50%		5.50%	5.50%	5.50%	5.50%	5.50%		5.50%		5.50%		5.50%
Stock options
Earnings Per Share
Stock options granted								698,500
Warrant Transaction Agreements
Earnings Per Share
Shares of common stock that can be purchased from warrants issued (in shares)																		55,286,696
Number of warrants exercised (in shares)			3,501,640	4,745,905	9,214,449			13,960,354
Warrants issued with the Walmart Stores, Inc transaction agreement
Earnings Per Share
Shares of common stock that can be purchased from warrants issued (in shares)																	55,286,696
Number of warrants exercised (in shares)				0	7,274,565	5,819,652		13,094,217
Stock options
Earnings Per Share
Number of dilutive potential common stock								9,165,066	16,273,120
Stock options granted				117,500			89,649	698,500	174,649
Restricted stock outstanding
Earnings Per Share
Number of dilutive potential common stock								6,511,808	4,455,484
Stock options granted				98,000			96,649	653,000	96,649
Warrants
Earnings Per Share
Number of dilutive potential common stock								83,518,821	110,573,392
Convertible senior notes
Earnings Per Share
Number of dilutive potential common stock								39,170,766	72,872,730