Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 41	$ 47	$ 68	$ 86
Deferred cumulative preferred stock dividends	0	(8)	0	(16)
Net income applicable to common stockholders	$ 41	$ 39	$ 68	$ 70
Weighted average shares
Weighted average common shares outstanding	57,101,816	56,574,796	57,012,208	56,544,256
Effect of dilutive securities
May Investor Warrants (in shares)	0	349,539	24,575	327,307
Stock-based awards (in shares)	1,037,122	826,895	1,069,287	751,518
Weighted average diluted common shares	58,138,938	57,751,230	58,106,070	57,623,081
Earnings per common share
Basic earnings per common share (in usd per share)	$ 0.72	$ 0.67	$ 1.18	$ 1.23
Effect of dilutive securities
May investors Warrants (in usd per share)	0.00	0.00	0.00	0.00
Stock-based awards (in usd per share)	(0.01)	(0.01)	(0.02)	(0.02)
Diluted (loss) earnings per share (in usd per share)	$ 0.71	$ 0.66	$ 1.16	$ 1.21