Financial Derivatives (Derivative Assets and Liabilitites Offsetting) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	$ 6,930	$ 4,941
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	5,235	3,802
Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	5,235	3,802
Derivative Liability, Fair Value Offset Amount	3,774	2,554
Derivative Liability, Cash Collateral	943	608
Derivative Liability, Net Fair Value	518	640
Derivative Liability, Net	518	640
Assets [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	6,930	4,941
Derivative Asset, Fair Value Offset Amount	3,774	2,554
Derivative Asset, Cash Collateral	646	551
Derivative Asset, Net Fair Value	2,510	1,836
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	297	180
Derivative Asset, Net	2,213	1,656
Interest Rate Contracts [Member] | Liability [Member] | Exchange Cleared, Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	1,923	855
Derivative Liability, Fair Value Offset Amount	1,651	779
Derivative Liability, Cash Collateral	243	57
Derivative Liability, Net Fair Value	29	19
Derivative Liability, Net	29	19
Interest Rate Contracts [Member] | Liability [Member] | Exchange Traded, Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	3	1
Derivative Liability, Net Fair Value	3	1
Derivative Liability, Net	3	1
Interest Rate Contracts [Member] | Liability [Member] | Over The Counter, Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	2,741	2,276
Derivative Liability, Fair Value Offset Amount	1,996	1,687
Derivative Liability, Cash Collateral	663	530
Derivative Liability, Net Fair Value	82	59
Derivative Liability, Net	82	59
Interest Rate Contracts [Member] | Assets [Member] | Exchange Cleared [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	1,844	1,003
Derivative Asset, Fair Value Offset Amount	1,651	779
Derivative Asset, Cash Collateral	152	195
Derivative Asset, Net Fair Value	41	29
Derivative Asset, Net	41	29
Interest Rate Contracts [Member] | Assets [Member] | Exchange Traded [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	2
Derivative Asset, Net Fair Value	2
Derivative Asset, Net	2
Interest Rate Contracts [Member] | Assets [Member] | Over The Counter [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	4,828	3,652
Derivative Asset, Fair Value Offset Amount	2,010	1,645
Derivative Asset, Cash Collateral	481	342
Derivative Asset, Net Fair Value	2,337	1,665
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	296	178
Derivative Asset, Net	2,041	1,487
Foreign Exchange [Member] | Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	245	204
Derivative Liability, Fair Value Offset Amount	123	85
Derivative Liability, Cash Collateral	35	20
Derivative Liability, Net Fair Value	87	99
Derivative Liability, Net	87	99
Foreign Exchange [Member] | Assets [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	253	284
Derivative Asset, Fair Value Offset Amount	112	129
Derivative Asset, Cash Collateral	12	13
Derivative Asset, Net Fair Value	129	142
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	1	2
Derivative Asset, Net	128	140
Credit Risk Contract [Member] | Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	6	4
Derivative Liability, Fair Value Offset Amount	4	3
Derivative Liability, Cash Collateral	2	1
Credit Risk Contract [Member] | Assets [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	3	2
Derivative Asset, Fair Value Offset Amount	1	1
Derivative Asset, Cash Collateral	1	1
Derivative Asset, Net Fair Value	1
Derivative Asset, Net	1
Other Contract [Member] | Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	317	462
Derivative Liability, Net Fair Value	317	462
Derivative Liability, Net	$ 317	$ 462