Income Taxes - Continuing Operations (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Provision for income taxes		$ 30	$ 36	$ 49	$ (157)	$ 48	$ 39	$ 35	$ 35	$ (42)	$ 157	$ 266
Income tax expense (benefit) included in common equity related to:
Unrealized gains (losses) on investment securities										274	128	(68)
Unrealized gains (losses) on fair value option liabilities attributable to our own credit spread										8	(98)	103
Unrealized gains (losses) on derivatives designated as cash flow hedges										23	3	12
Employer accounting for post-retirement plans										(1)	(5)	3
Stockholders' Equity Attributable to Parent, Attributable to Common Stockholders		$ 17,026				$ 16,991				17,026	16,991	19,241
Total income taxes										$ 262	$ 185	$ 407
Cumulative Effect, Period of Adoption, Adjustment [Member]
Income tax expense (benefit) included in common equity related to:
Stockholders' Equity Attributable to Parent, Attributable to Common Stockholders	[1]												$ 91

[1] Reflects the adoption of new accounting guidance in 2018 which resulted in a cumulative effect adjustment as of January 1, 2018 to reclassify the stranded tax effects resulting from the change in the Federal corporate income tax rate from accumulated other comprehensive income (loss) to retained earnings.