Capital Stock - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Oct. 01, 2019	Sep. 30, 2019	Nov. 14, 2018
Class of Stock [Line Items]
Preferred Stock, Shares Authorized	55,000,000		55,000,000
Preferred stock, par value (in usd per share)	$ 0.01		$ 0.01
Proceeds from Issuance of Preferred Stock and Preference Stock			$ 121,000,000	$ 0
Strategic Partnership Interest on As-Converted Basis	900.00%		900.00%
Document Period End Date			Mar. 31, 2020
Preferred Stock, Value, Outstanding	$ 127,000,000		$ 127,000,000			$ 0
Dividends, Preferred Stock	$ 1,000,000	$ 1,000,000	$ 2,000,000
Strategic Partnership, Minimum Shares Required for Consent Rights			4,759,339
Preferred shares issued	125,000		125,000			0
Common stock, shares authorized	550,000,000		550,000,000			550,000,000
Common stock, par value (usd per share)	$ 0.01		$ 0.01			$ 0.01
Common stock, shares issued	82,654,594		82,654,594			111,046,085
Common stock, shares outstanding	82,654,594		82,654,594			111,033,405
Common stock, issued for GUC (shares)						12,680
Warrant repurchase program, authorized amount							$ 15,000,000
Warrant Repurchase Program, Number of Securities Called by Warrants or Rights, Number of Warrants Repurchased	$ 0		$ 0
Stock Repurchase Program, Authorized Amount					$ 500,000,000
Stock Repurchased During Period, Shares	18,206,273		28,923,664
Stock Repurchased During Period, Value	$ 10.89		$ 11.41
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased	170,000,000		170,000,000
As Previously Reported
Class of Stock [Line Items]
Common stock, shares issued	82,654,594		82,654,594			111,046,085
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in usd per share)	$ 0.01		$ 0.01
Proceeds from Issuance of Preferred Stock and Preference Stock			$ 125,000,000
Price per share of common stock (in usd per share)	$ 16.00		$ 16.00