Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Assets
Investment securities – available for sale	$ 69,057	$ 63,389
Mortgage servicing rights	1,483	1,983
Financial derivatives	2,834	1,052
Liabilities
Financial derivatives	672	1,063
Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	69,057	63,389
Loans	754	782
Equity investments	2,177	2,209
Trading securities	3,097	3,916
Financial derivatives	4,638	2,081
Other assets	452	493
Total Assets	83,193	75,744
Liabilities
Other borrowed funds	820	1,007
Financial derivatives	2,332	2,290
Other liabilities	105	58
Total liabilities	3,257	3,355
Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	17,725	17,753
Equity investments	590	751
Trading securities	854	2,137
Financial derivatives	2	3
Other assets	323	291
Total Assets	19,494	20,935
Liabilities
Other borrowed funds	723	868
Financial derivatives	3	1
Total liabilities	726	869
Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	49,150	43,150
Loans	425	510
Trading securities	2,243	1,777
Financial derivatives	4,546	2,053
Other assets	129	157
Total Assets	57,952	48,449
Liabilities
Other borrowed funds	91	132
Financial derivatives	2,123	2,021
Total liabilities	2,214	2,153
Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	2,182	2,486
Loans	329	272
Equity investments	1,390	1,255
Trading securities		2
Financial derivatives	90	25
Other assets		45
Total Assets	5,550	6,157
Liabilities
Other borrowed funds	6	7
Financial derivatives	206	268
Other liabilities	105	58
Total liabilities	317	333
Residential Mortgage [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Loans held for sale	785	495
Mortgage servicing rights	888	1,257
Residential Mortgage [Member] \| Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Loans held for sale	781	493
Residential Mortgage [Member] \| Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Loans held for sale	4	2
Mortgage servicing rights	888	1,257
Commercial Mortgage [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Loans held for sale	750	396
Mortgage servicing rights	595	726
Commercial Mortgage [Member] \| Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Loans held for sale	678	309
Commercial Mortgage [Member] \| Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Loans held for sale	72	87
Mortgage servicing rights	595	726
US Treasury and Government [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	18,005	18,100
US Treasury and Government [Member] \| Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	17,725	17,753
US Treasury and Government [Member] \| Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	280	347
Residential Mortgage-backed Securities [Member] \| Mortgage-backed Securities Agency [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	34,580	28,993
Residential Mortgage-backed Securities [Member] \| Mortgage-backed Securities Non-agency [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	1,931	2,211
Residential Mortgage-backed Securities [Member] \| Level 2 [Member] \| Mortgage-backed Securities Agency [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	34,580	28,993
Residential Mortgage-backed Securities [Member] \| Level 2 [Member] \| Mortgage-backed Securities Non-agency [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	78	83
Residential Mortgage-backed Securities [Member] \| Level 3 [Member] \| Mortgage-backed Securities Non-agency [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	1,853	2,128
Commercial Mortgage Backed Securities [Member] \| Mortgage-backed Securities Agency [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	2,939	2,577
Commercial Mortgage Backed Securities [Member] \| Mortgage-backed Securities Non-agency [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	3,246	2,657
Commercial Mortgage Backed Securities [Member] \| Level 2 [Member] \| Mortgage-backed Securities Agency [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	2,939	2,577
Commercial Mortgage Backed Securities [Member] \| Level 2 [Member] \| Mortgage-backed Securities Non-agency [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	3,246	2,657
Asset backed [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	5,339	4,972
Asset backed [Member] \| Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	5,087	4,698
Asset backed [Member] \| Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	252	274
Other [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	3,017	3,879
Other [Member] \| Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	2,940	3,795
Other [Member] \| Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Assets
Investment securities – available for sale	$ 77	$ 84

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