Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Balance at beginning of period at Dec. 31, 2017	$ 4,409	$ 107	$ 3	$ 4,033	$ 368	$ (83)	$ (19)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	61				87	(26)
Dividends declared:
Preferred stock	(2)				(2)
Common stock: $0.12/share	(39)				(39)
Issuance of common stock	2			2
Restricted stock compensation	2			2
Balance at end of period at Mar. 31, 2018	4,433	107	3	4,037	414	(109)	(19)
Balance at beginning of period at Dec. 31, 2018	4,608	107	3	4,049	576	(106)	(21)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	112				94	18
Dividends declared:
Preferred stock	(2)				(2)
Common stock: $0.12/share	(39)				(39)
Issuance of common stock	(1)			1			(2)
Restricted stock compensation	2			2
Balance at end of period at Mar. 31, 2019	$ 4,680	$ 107	$ 3	$ 4,052	$ 629	$ (88)	$ (23)