Fair Value Disclosures - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets
AFS securities	$ 25,038	$ 24,547
LHFS at fair value	988	1,099
MSRs	1,108	1,056
Trading and equity securities	767	633
Derivative assets	246	443
Private equity investments	393	404
Total assets	28,540	28,182
Liabilities
Derivative liabilities	247	714
Securities sold short	145	120
Total liabilities	392	834
Level 1
Assets
AFS securities	0	6
LHFS at fair value	0	0
MSRs	0	0
Trading and equity securities	374	363
Derivative assets	0	0
Private equity investments	0	0
Total assets	374	369
Liabilities
Derivative liabilities	1	0
Securities sold short	0	0
Total liabilities	1	0
Level 2
Assets
AFS securities	24,647	24,109
LHFS at fair value	988	1,099
MSRs	0	0
Trading and equity securities	390	270
Derivative assets	234	437
Private equity investments	0	0
Total assets	26,259	25,915
Liabilities
Derivative liabilities	246	711
Securities sold short	145	120
Total liabilities	391	831
Level 3
Assets
AFS securities	391	432
LHFS at fair value	0	0
MSRs	1,108	1,056
Trading and equity securities	3	0
Derivative assets	12	6
Private equity investments	393	404
Total assets	1,907	1,898
Liabilities
Derivative liabilities	0	3
Securities sold short	0	0
Total liabilities	0	3
U.S. Treasury
Assets
AFS securities	3,441	2,291
U.S. Treasury \| Level 1
Assets
AFS securities	0	0
U.S. Treasury \| Level 2
Assets
AFS securities	3,441	2,291
U.S. Treasury \| Level 3
Assets
AFS securities	0	0
GSE
Assets
AFS securities	200	179
GSE \| Level 1
Assets
AFS securities	0	0
GSE \| Level 2
Assets
AFS securities	200	179
GSE \| Level 3
Assets
AFS securities	0	0
Agency MBS
Assets
AFS securities	20,155	20,101
Agency MBS \| Level 1
Assets
AFS securities	0	0
Agency MBS \| Level 2
Assets
AFS securities	20,155	20,101
Agency MBS \| Level 3
Assets
AFS securities	0	0
States and political subdivisions
Assets
AFS securities	701	1,392
States and political subdivisions \| Level 1
Assets
AFS securities	0	0
States and political subdivisions \| Level 2
Assets
AFS securities	701	1,392
States and political subdivisions \| Level 3
Assets
AFS securities	0	0
Non-agency MBS
Assets
AFS securities	505	576
Non-agency MBS \| Level 1
Assets
AFS securities	0	0
Non-agency MBS \| Level 2
Assets
AFS securities	114	144
Non-agency MBS \| Level 3
Assets
AFS securities	391	432
Other
Assets
AFS securities	36	8
Other \| Level 1
Assets
AFS securities	0	6
Other \| Level 2
Assets
AFS securities	36	2
Other \| Level 3
Assets
AFS securities	$ 0	$ 0

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