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, 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 (Note 11)	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 (Note 11)	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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,567					1,567
Other comprehensive income (loss)	(53)				(53)
Stock based compensation	43			43
Dividends paid (Note 11)	(445)					(445)
Dividends declared on preferred stock (Note 11)	(45)					(45)
Balance at end of period at Dec. 31, 2019	$ 12,726	$ 0	$ 0	$ 8,101	$ (1,119)	$ 5,744