Financial Derivatives (Derivatives Not Designated As Hedging Instruments under GAAP) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Derivative Notional Amount	$ 368,496	$ 347,976
Derivative Asset, Fair Value	6,930	4,941
Derivative Liability, Fair Value	5,235	3,802
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Notional Amount	51,508	52,074
Derivative Asset, Fair Value	1,663	1,159
Derivative Liability, Fair Value	301	174
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Notional Amount	316,988	295,902
Derivative Asset, Fair Value	5,267	3,782
Derivative Liability, Fair Value	4,934	3,628
Not Designated as Hedging Instrument [Member] | Residential Mortgages [Member]
Derivative [Line Items]
Derivative Notional Amount	88,207	73,891
Derivative Asset, Fair Value	1,308	823
Derivative Liability, Fair Value	838	447
Not Designated as Hedging Instrument [Member] | Residential Mortgages [Member] | Residential Mortgage Servicing Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	80,934	65,728
Derivative Asset, Fair Value	1,278	789
Derivative Liability, Fair Value	824	439
Not Designated as Hedging Instrument [Member] | Residential Mortgages [Member] | Loan Sales Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	7,273	8,163
Derivative Asset, Fair Value	30	34
Derivative Liability, Fair Value	14	8
Not Designated as Hedging Instrument [Member] | Commercial Mortgage Banking [Member]
Derivative [Line Items]
Derivative Notional Amount	21,074	24,091
Derivative Asset, Fair Value	143	88
Derivative Liability, Fair Value	76	52
Not Designated as Hedging Instrument [Member] | Commercial Mortgage Banking [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Derivative Notional Amount	58	77
Not Designated as Hedging Instrument [Member] | Commercial Mortgage Banking [Member] | Commercial Mortgage Banking Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	21,016	24,014
Derivative Asset, Fair Value	143	88
Derivative Liability, Fair Value	76	52
Not Designated as Hedging Instrument [Member] | Customer Contracts [Member]
Derivative [Line Items]
Derivative Notional Amount	202,157	192,621
Derivative Asset, Fair Value	3,800	2,812
Derivative Liability, Fair Value	3,615	2,661
Not Designated as Hedging Instrument [Member] | Customer Contracts [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	11,261	10,888
Derivative Asset, Fair Value	178	194
Derivative Liability, Fair Value	157	198
Not Designated as Hedging Instrument [Member] | Customer Contracts [Member] | Risk Participation Agreement [Member]
Derivative [Line Items]
Derivative Notional Amount	5,775	5,026
Derivative Asset, Fair Value	3	2
Derivative Liability, Fair Value	6	4
Not Designated as Hedging Instrument [Member] | Customer Contracts [Member] | Customer Related Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	185,121	176,707
Derivative Asset, Fair Value	3,619	2,616
Derivative Liability, Fair Value	3,452	2,459
Not Designated as Hedging Instrument [Member] | Other Risk Management Activity [Member]
Derivative [Line Items]
Derivative Notional Amount	5,550	5,299
Derivative Asset, Fair Value	16	59
Derivative Liability, Fair Value	405	468
Not Designated as Hedging Instrument [Member] | Other Risk Management Activity [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	2,995	2,742
Derivative Asset, Fair Value	16	59
Derivative Liability, Fair Value	88	6
Not Designated as Hedging Instrument [Member] | Other Risk Management Activity [Member] | Other Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	2,555	2,557
Derivative Liability, Fair Value	317	462
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Residential Mortgage Servicing Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	36,925	37,505
Derivative Asset, Fair Value	1,225	758
Derivative Liability, Fair Value	793	416
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Commercial Mortgage Banking Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	4,186	3,945
Derivative Asset, Fair Value	129	77
Derivative Liability, Fair Value	68	46
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Customer Related Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	163,175	157,041
Derivative Asset, Fair Value	3,445	2,507
Derivative Liability, Fair Value	3,424	2,433
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member] | Residential Mortgage Servicing Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	1,103	650
Derivative Asset, Fair Value	39	27
Derivative Liability, Fair Value	23	14
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member] | Commercial Mortgage Banking Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount		439
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member] | Customer Related Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	4,963	4,363
Derivative Asset, Fair Value	144	86
Derivative Liability, Fair Value	11	13
Not Designated as Hedging Instrument [Member] | Future [Member] | Residential Mortgage Servicing Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	20,626	17,653
Not Designated as Hedging Instrument [Member] | Future [Member] | Loan Sales Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	10	20
Not Designated as Hedging Instrument [Member] | Future [Member] | Commercial Mortgage Banking Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	15,450	18,454
Not Designated as Hedging Instrument [Member] | Future [Member] | Customer Related Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	1,632	1,673
Not Designated as Hedging Instrument [Member] | Future Options [Member] | Residential Mortgage Servicing Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	18,000	6,000
Derivative Asset, Fair Value	2
Derivative Liability, Fair Value	3	1
Not Designated as Hedging Instrument [Member] | Residential Mortgage Loan Commitment [Member] | Loan Sales Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	1,950	1,580
Derivative Asset, Fair Value	22	16
Not Designated as Hedging Instrument [Member] | Commercial Mortgage Loan Commitment [Member] | Commercial Mortgage Banking Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	1,380	1,176
Derivative Asset, Fair Value	14	11
Derivative Liability, Fair Value	8	6
Not Designated as Hedging Instrument [Member] | Bond Option [Member] | Loan Sales Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	200	200
Derivative Asset, Fair Value		2
Not Designated as Hedging Instrument [Member] | Caps Floors Sold [Member] | Customer Related Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	5,277	5,337
Derivative Liability, Fair Value	7	11
Not Designated as Hedging Instrument [Member] | Caps Floors Purchased [Member] | Customer Related Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	6,617	6,383
Derivative Asset, Fair Value	19	18
Not Designated as Hedging Instrument [Member] | Mortgage Backed Securities Commitments [Member] | Residential Mortgage Servicing Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	4,280	3,920
Derivative Asset, Fair Value	12	4
Derivative Liability, Fair Value	5	8
Not Designated as Hedging Instrument [Member] | Mortgage Backed Securities Commitments [Member] | Loan Sales Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	5,113	6,363
Derivative Asset, Fair Value	8	16
Derivative Liability, Fair Value	14	8
Not Designated as Hedging Instrument [Member] | Mortgage Backed Securities Commitments [Member] | Customer Related Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Notional Amount	3,457	1,910
Derivative Asset, Fair Value	11	5
Derivative Liability, Fair Value	$ 10	$ 2