Fair Value Disclosures - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Assets
Trading securities	$ 992	$ 1,180
AFS securities at fair value	29,449	25,297
LHFS	2,664	1,035
MSRs	828	880
Derivative assets	1,267	970
Private equity and similar investments	340	289
Total assets	35,540	29,651
Liabilities [Abstract]
Derivative liabilities	1,187	792
Securities sold short	181	147
Total liabilities	1,368	939
Level 1
Assets
Trading securities	318	311
Total assets	328	315
Level 2
Assets
Trading securities	674	869
LHFS	2,664	1,035
Total assets	33,483	27,533
Liabilities [Abstract]
Securities sold short	181	147
Total liabilities	1,366	935
Level 3
Assets
MSRs	828	880
Private equity and similar investments	340	289
Total assets	1,729	1,803
Liabilities [Abstract]
Total liabilities	2	4
U.S. Treasury
Assets
AFS securities at fair value	2,650	1,832
U.S. Treasury \| Level 2
Assets
AFS securities at fair value	2,650	1,832
GSE
Assets
AFS securities at fair value	176	51
GSE \| Level 1
Assets
AFS securities at fair value	0
GSE \| Level 2
Assets
AFS securities at fair value	176	51
GSE \| Level 3
Assets
AFS securities at fair value	0
Agency MBS
Assets
AFS securities at fair value	23,535	20,046
Agency MBS \| Level 2
Assets
AFS securities at fair value	23,535	20,046
States and political subdivisions
Assets
AFS securities at fair value	2,356	2,375
States and political subdivisions \| Level 2
Assets
AFS securities at fair value	2,356	2,375
Non-agency MBS
Assets
AFS securities at fair value	722	989
Non-agency MBS \| Level 2
Assets
AFS securities at fair value	183	363
Non-agency MBS \| Level 3
Assets
AFS securities at fair value	539	626
Other
Assets
AFS securities at fair value	10	4
Other \| Level 1
Assets
AFS securities at fair value	10	4
Interest rate contracts
Assets
Derivative assets	1,264	964
Liabilities [Abstract]
Derivative liabilities	1,184	788
Interest rate contracts \| Level 2
Assets
Derivative assets	1,242	956
Liabilities [Abstract]
Derivative liabilities	1,182	784
Interest rate contracts \| Level 3
Assets
Derivative assets	22	8
Liabilities [Abstract]
Derivative liabilities	2	4
Foreign exchange contracts
Assets
Derivative assets	3	6
Liabilities [Abstract]
Derivative liabilities	3	4
Foreign exchange contracts \| Level 2
Assets
Derivative assets	3	6
Liabilities [Abstract]
Derivative liabilities	$ 3	$ 4

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value of obligations incurred from short sales.

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