Earnings Per Share - Dilutive Potential Common Shares (Details) - USD ($) $ in Thousands				1 Months Ended			3 Months Ended	12 Months Ended
	Jul. 01, 2020	Nov. 01, 2018	May 16, 2013	Jan. 31, 2020	Jul. 31, 2017	Apr. 30, 2017	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 31, 2020	May 18, 2020	Sep. 30, 2019	Mar. 31, 2018	Apr. 04, 2017
Earnings Per Share
Number of dilutive potential common stock								163,169,490	200,327,965	201,692,250
Interest rate (as a percent)											3.50%
Convertible senior notes							$ 85,600	$ 85,600
Stock options
Earnings Per Share
Stock options granted								3,509,549	3,221,892	2,679,667
Warrant Transaction Agreements
Earnings Per Share
Shares of common stock that can be purchased from warrants issued (in shares)					55,286,696	55,286,696									55,286,696
Number of warrants exercised (in shares)					5,819,652	0
Tranche one of warrants issued with the Amazon.com, Inc transaction agreement
Earnings Per Share
Shares of common stock that can be purchased from warrants issued (in shares)															5,819,652
Series C Preferred Stock
Earnings Per Share
Shares issued (in shares)			10,431
Series E Preferred Stock
Earnings Per Share
Shares issued (in shares)		35,000
Number of shares redeemed									4,038
Number of preferred shares that had been converted to common stock				500					30,462
5.5% Convertible Senior Notes
Earnings Per Share
Interest rate (as a percent)							5.50%	5.50%			5.50%	5.50%		5.50%
Conversion of notes through common stock issuance							14,600,000
Repurchase amount											$ 66,300
Convertible senior notes							$ 33,500	$ 33,500
Long-term borrowings							$ 160	$ 160			$ 48,700
7.5% Convertible Senior Note
Earnings Per Share
Interest rate (as a percent)	7.50%						7.50%	7.50%					7.50%
Conversion of notes through common stock issuance	16,000,000.0
Stock options
Earnings Per Share
Number of dilutive potential common stock								10,284,498	23,013,590	21,957,150
Stock options granted								3,509,549	3,221,892	2,679,667
Restricted stock
Earnings Per Share
Number of dilutive potential common stock								5,874,642	4,608,560	2,347,347
Stock options granted								3,227,149	3,201,892	2,367,347
Warrants
Earnings Per Share
Number of dilutive potential common stock								104,753,740	110,573,392	115,824,142
Preferred stock
Earnings Per Share
Number of dilutive potential common stock									2,998,527	17,933,591
Convertible Senior Notes
Earnings Per Share
Number of dilutive potential common stock								42,256,610	59,133,896	43,630,020