Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 57	$ 47	$ 143	$ 125
Deferred cumulative preferred stock dividends	(2)	(8)	(18)	(22)
Net income applicable to common stockholders	$ 55	$ 39	$ 125	$ 103
Weighted average shares
Weighted average common shares outstanding	56,580,238	56,436,026	56,556,188	56,419,354
Effect of dilutive securities
May Investor warrants (in shares)	364,791	339,478	339,893	290,840
Stock-based awards (in shares)	988,777	431,999	831,181	340,595
Weighted average diluted common shares	57,933,806	57,207,503	57,727,262	57,050,789
Earnings per common share
Basic earnings per common share (in usd per share)	$ 0.98	$ 0.70	$ 2.21	$ 1.82
Effect of dilutive securities
May investors warrants (in usd per share)	0.00	0.00	(0.02)	(0.01)
Stock-based awards (in usd per share)	(0.02)	(0.01)	(0.03)	(0.01)
Diluted (loss) earnings per share (in usd per share)	$ 0.96	$ 0.69	$ 2.16	$ 1.80