Financial Derivatives (Derivative Assets and Liabilitites Offsetting) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	$ 7,147	$ 4,941
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	5,407	3,802
Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	5,407	3,802
Derivative Liability, Fair Value Offset Amount	3,851	2,554
Derivative Liability, Cash Collateral	1,045	608
Derivative Liability, Net Fair Value	511	640
Derivative Liability, Net	511	640
Assets [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	7,147	4,941
Derivative Asset, Fair Value Offset Amount	3,851	2,554
Derivative Asset, Cash Collateral	782	551
Derivative Asset, Net Fair Value	2,514	1,836
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	314	180
Derivative Asset, Net	2,200	1,656
Interest Rate Contracts [Member] | Liability [Member] | Exchange Cleared, Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	2,192	855
Derivative Liability, Fair Value Offset Amount	1,794	779
Derivative Liability, Cash Collateral	376	57
Derivative Liability, Net Fair Value	22	19
Derivative Liability, Net	22	19
Interest Rate Contracts [Member] | Liability [Member] | Exchange Traded, Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value		1
Derivative Liability, Net Fair Value		1
Derivative Liability, Net		1
Interest Rate Contracts [Member] | Liability [Member] | Over The Counter, Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	2,647	2,276
Derivative Liability, Fair Value Offset Amount	1,947	1,687
Derivative Liability, Cash Collateral	643	530
Derivative Liability, Net Fair Value	57	59
Derivative Liability, Net	57	59
Interest Rate Contracts [Member] | Assets [Member] | Exchange Cleared [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	2,002	1,003
Derivative Asset, Fair Value Offset Amount	1,793	779
Derivative Asset, Cash Collateral	184	195
Derivative Asset, Net Fair Value	25	29
Derivative Asset, Net	25	29
Interest Rate Contracts [Member] | Assets [Member] | Over The Counter [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	4,750	3,652
Derivative Asset, Fair Value Offset Amount	1,844	1,645
Derivative Asset, Cash Collateral	557	342
Derivative Asset, Net Fair Value	2,349	1,665
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	314	178
Derivative Asset, Net	2,035	1,487
Foreign Exchange [Member] | Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	184	204
Derivative Liability, Fair Value Offset Amount	105	85
Derivative Liability, Cash Collateral	24	20
Derivative Liability, Net Fair Value	55	99
Derivative Liability, Net	55	99
Foreign Exchange [Member] | Assets [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	392	284
Derivative Asset, Fair Value Offset Amount	213	129
Derivative Asset, Cash Collateral	40	13
Derivative Asset, Net Fair Value	139	142
Derivative Asset, Securities Collateral Held Under Master Netting Agreements		2
Derivative Asset, Net	139	140
Credit Risk Contract [Member] | Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	7	4
Derivative Liability, Fair Value Offset Amount	5	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	377	462
Derivative Liability, Net Fair Value	377	462
Derivative Liability, Net	$ 377	$ 462