Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period	12 years
Assets
Total debt securities	$ 63,389	$ 57,033
Securities available for sale, fair value	63,389	57,618
Mortgage servicing rights	1,983	1,832
Fair Value, Measurements, Recurring
Assets
Total debt securities	63,389	57,033
Securities available for sale, fair value	63,389	57,618
Loans	782	869
Equity investments	2,209	1,265
Trading securities	3,916	2,915
Financial derivatives	2,081	2,874
Other assets	493	638
Total Assets	75,744	69,673
Liabilities
Other borrowed funds	1,007	1,344
Financial derivatives	2,290	2,856
Other liabilities	58	33
Total liabilities	3,355	4,233
Residential Mortgage \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	495	832
Mortgage servicing rights	1,257	1,164
Commercial Mortgage \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	396	830
Mortgage servicing rights	726	668
US Treasury and Government Agencies Securities \| Fair Value, Measurements, Recurring
Assets
Total debt securities	18,100	14,521
Residential mortgage-backed Securities \| Mortgage-backed Securities Agency \| Fair Value, Measurements, Recurring
Assets
Total debt securities	28,993	25,406
Residential mortgage-backed Securities \| Mortgage-backed Securities Non-agency \| Fair Value, Measurements, Recurring
Assets
Total debt securities	2,211	2,758
Commercial Mortgage Backed Securities \| Mortgage-backed Securities Agency \| Fair Value, Measurements, Recurring
Assets
Total debt securities	2,577	1,904
Commercial Mortgage Backed Securities \| Mortgage-backed Securities Non-agency \| Fair Value, Measurements, Recurring
Assets
Total debt securities	2,657	2,613
Asset backed \| Fair Value, Measurements, Recurring
Assets
Total debt securities	4,972	5,397
Other Debt Obligations \| Fair Value, Measurements, Recurring
Assets
Total debt securities	3,879	4,434
Other Assets \| Fair Value, Measurements, Recurring
Assets
Securities available for sale, fair value		585
Level 1 \| Fair Value, Measurements, Recurring
Assets
Total debt securities	17,753	14,088
Securities available for sale, fair value	17,753	14,612
Equity investments	751
Trading securities	2,137	1,243
Financial derivatives	3
Other assets	291	278
Total Assets	20,935	16,133
Liabilities
Other borrowed funds	868	1,079
Financial derivatives	1
Total liabilities	869	1,079
Level 1 \| US Treasury and Government Agencies Securities \| Fair Value, Measurements, Recurring
Assets
Total debt securities	17,753	14,088
Level 1 \| Other Assets \| Fair Value, Measurements, Recurring
Assets
Securities available for sale, fair value		524
Level 2 \| Fair Value, Measurements, Recurring
Assets
Total debt securities	43,150	39,865
Securities available for sale, fair value	43,150	39,926
Loans	510	571
Trading securities	1,777	1,670
Financial derivatives	2,053	2,864
Other assets	157	253
Total Assets	48,449	46,836
Liabilities
Other borrowed funds	132	254
Financial derivatives	2,021	2,369
Total liabilities	2,153	2,623
Level 2 \| Residential Mortgage \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	493	829
Level 2 \| Commercial Mortgage \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	309	723
Level 2 \| US Treasury and Government Agencies Securities \| Fair Value, Measurements, Recurring
Assets
Total debt securities	347	433
Level 2 \| Residential mortgage-backed Securities \| Mortgage-backed Securities Agency \| Fair Value, Measurements, Recurring
Assets
Total debt securities	28,993	25,406
Level 2 \| Residential mortgage-backed Securities \| Mortgage-backed Securities Non-agency \| Fair Value, Measurements, Recurring
Assets
Total debt securities	83	97
Level 2 \| Commercial Mortgage Backed Securities \| Mortgage-backed Securities Agency \| Fair Value, Measurements, Recurring
Assets
Total debt securities	2,577	1,904
Level 2 \| Commercial Mortgage Backed Securities \| Mortgage-backed Securities Non-agency \| Fair Value, Measurements, Recurring
Assets
Total debt securities	2,657	2,613
Level 2 \| Asset backed \| Fair Value, Measurements, Recurring
Assets
Total debt securities	4,698	5,065
Level 2 \| Other Debt Obligations \| Fair Value, Measurements, Recurring
Assets
Total debt securities	3,795	4,347
Level 2 \| Other Assets \| Fair Value, Measurements, Recurring
Assets
Securities available for sale, fair value		61
Level 3 \| Fair Value, Measurements, Recurring
Assets
Total debt securities	2,486	3,080
Securities available for sale, fair value	2,486	3,080
Loans	272	298
Equity investments	1,255	1,036
Trading securities	2	2
Financial derivatives	25	10
Other assets	45	107
Total Assets	6,157	6,475
Liabilities
Other borrowed funds	7	11
Financial derivatives	268	487
Other liabilities	58	33
Total liabilities	333	531
Level 3 \| Residential Mortgage \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	2	3
Mortgage servicing rights	1,257	1,164
Level 3 \| Commercial Mortgage \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	87	107
Mortgage servicing rights	726	668
Level 3 \| Residential mortgage-backed Securities \| Mortgage-backed Securities Non-agency \| Fair Value, Measurements, Recurring
Assets
Total debt securities	2,128	2,661
Level 3 \| Asset backed \| Fair Value, Measurements, Recurring
Assets
Total debt securities	274	332
Level 3 \| Other Debt Obligations \| Fair Value, Measurements, Recurring
Assets
Total debt securities	$ 84	$ 87

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