Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Preferred Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Retained Earnings [Member]
Balance at beginning of period at Dec. 31, 2017	$ 10,294	$ 0	$ 0	$ 7,525	$ (768)	$ 3,537
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of accounting standards	40					40
Net income	369					369
Other comprehensive income	60				60
Stock based compensation	16			16
Dividends paid	(30)					(30)
Other	(1)					(1)
Balance at end of period at Mar. 31, 2018	10,748	0	0	7,541	(708)	3,915
Balance at beginning of period at Dec. 31, 2018	11,659	0	0	8,058	(1,066)	4,667
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	271					271
Other comprehensive income	42				42
Stock based compensation	11			11
Other	1					1
Balance at end of period at Mar. 31, 2019	$ 11,984	$ 0	$ 0	$ 8,069	$ (1,024)	$ 4,939