Income Taxes - Continuing Operations (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes		$ 34	$ 58	$ 82	$ 92	$ 907	$ 61	$ 108	$ 152	$ 266	$ 1,228	$ 89
Income tax expense (benefit) included in common equity related to:
Unrealized gains (losses) on investment securities										(68)	127	(135)
Unrealized gains (losses) on fair value option liabilities attributable to our own credit spread(1)	[1]									103	(115)	0
Unrealized gains (losses) on derivatives designated as cash flow hedges										12	(5)	9
Employer accounting for post-retirement plans										3	1	2
Cumulative effective adjustment to initially apply new accounting guidance for stranded tax effects resulting from Tax Legislation(2)	[2]					$ 0					0	0	$ 91
Total income taxes										$ 407	$ 1,236	$ (35)

[1] As a result of adopting new accounting guidance in 2017, beginning January 1, 2017, the fair value movement on fair value option liabilities attributable to our own credit spread is recorded in common equity as a component of other comprehensive income (loss).

[2] See Note 2, "Summary of Significant Accounting Polices and New Accounting Pronouncements," for additional discussion.