Fair Value Disclosures - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets
AFS securities	$ 26,315	$ 25,038
LHFS at fair value	834	988
MSRs	1,036	1,108
Trading and equity securities	1,898	767
Derivative assets	338	246
Private equity investments	388	393
Total assets	30,809	28,540
Liabilities
Derivative liabilities	180	247
Securities sold short	250	145
Total liabilities	430	392
Level 1
Assets
AFS securities	0	0
LHFS at fair value	0	0
MSRs	0	0
Trading and equity securities	371	374
Derivative assets	1	0
Private equity investments	0	0
Total assets	372	374
Liabilities
Derivative liabilities	0	1
Securities sold short	0	0
Total liabilities	0	1
Level 2
Assets
AFS securities	25,929	24,647
LHFS at fair value	834	988
MSRs	0	0
Trading and equity securities	1,516	390
Derivative assets	327	234
Private equity investments	0	0
Total assets	28,606	26,259
Liabilities
Derivative liabilities	177	246
Securities sold short	250	145
Total liabilities	427	391
Level 3
Assets
AFS securities	386	391
LHFS at fair value	0	0
MSRs	1,036	1,108
Trading and equity securities	11	3
Derivative assets	10	12
Private equity investments	388	393
Total assets	1,831	1,907
Liabilities
Derivative liabilities	3	0
Securities sold short	0	0
Total liabilities	3	0
U.S. Treasury
Assets
AFS securities	1,878	3,441
U.S. Treasury \| Level 1
Assets
AFS securities	0	0
U.S. Treasury \| Level 2
Assets
AFS securities	1,878	3,441
U.S. Treasury \| Level 3
Assets
AFS securities	0	0
GSE
Assets
AFS securities	233	200
GSE \| Level 1
Assets
AFS securities	0	0
GSE \| Level 2
Assets
AFS securities	233	200
GSE \| Level 3
Assets
AFS securities	0	0
Agency MBS
Assets
AFS securities	23,047	20,155
Agency MBS \| Level 1
Assets
AFS securities	0	0
Agency MBS \| Level 2
Assets
AFS securities	23,047	20,155
Agency MBS \| Level 3
Assets
AFS securities	0	0
States and political subdivisions
Assets
AFS securities	626	701
States and political subdivisions \| Level 1
Assets
AFS securities	0	0
States and political subdivisions \| Level 2
Assets
AFS securities	626	701
States and political subdivisions \| Level 3
Assets
AFS securities	0	0
Non-agency MBS
Assets
AFS securities	497	505
Non-agency MBS \| Level 1
Assets
AFS securities	0	0
Non-agency MBS \| Level 2
Assets
AFS securities	111	114
Non-agency MBS \| Level 3
Assets
AFS securities	386	391
Other
Assets
AFS securities	34	36
Other \| Level 1
Assets
AFS securities	0	0
Other \| Level 2
Assets
AFS securities	34	36
Other \| Level 3
Assets
AFS securities	$ 0	$ 0

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