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, 2015	$ 8,052	$ 0	$ 0	$ 6,484	$ (1,104)	$ 2,672
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	754					754
Other comprehensive income (loss)	(134)				(134)
Stock based compensation	21			21
Balance at end of period at Dec. 31, 2016	8,693	0	0	6,505	(1,238)	3,426
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	661					661
Other comprehensive income (loss)	470				470
Stock based compensation	35			35
Issuance of preferred stock	985			985
Dividends paid (Note 11)	(550)					(550)
Balance at end 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 (Note 1)	40					40
Net income	1,570					1,570
Other comprehensive income (loss)	(298)				(298)
Stock based compensation	41			41
Issuance of preferred stock	492			492
Dividends paid (Note 11)	(434)					(434)
Dividends declared on preferred stock (Note 11)	(46)					(46)
Balance at end of period at Dec. 31, 2018	$ 11,659	$ 0	$ 0	$ 8,058	$ (1,066)	$ 4,667