Financial Derivatives (Derivative Assets and Liabilitites Offsetting) (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	$ 4,941,000,000	$ 5,234,000,000
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	3,802,000,000	4,027,000,000
Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	3,802,000,000	4,027,000,000
Derivative Liability, Fair Value Offset Amount	2,554,000,000	2,141,000,000
Derivative Liability, Cash Collateral	608,000,000	503,000,000
Derivative Liability, Net Fair Value	640,000,000	1,383,000,000
Derivative Liability, Net	640,000,000	1,383,000,000
Assets [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	4,941,000,000	5,234,000,000
Derivative Asset, Fair Value Offset Amount	2,554,000,000	2,141,000,000
Derivative Asset, Cash Collateral	551,000,000	506,000,000
Derivative Asset, Net Fair Value	1,836,000,000	2,587,000,000
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	180,000,000	144,000,000
Derivative Asset, Net	1,656,000,000	2,443,000,000
Interest Rate Contracts [Member] | Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value		3,272,000,000
Derivative Liability, Fair Value Offset Amount		2,057,000,000
Derivative Liability, Cash Collateral		483,000,000
Derivative Liability, Net Fair Value		732,000,000
Derivative Liability, Net		732,000,000
Interest Rate Contracts [Member] | Liability [Member] | Exchange Cleared, Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	855,000,000	657,000,000
Derivative Liability, Fair Value Offset Amount	779,000,000
Derivative Liability, Cash Collateral	57,000,000
Derivative Liability, Net Fair Value	19,000,000
Derivative Liability, Net	19,000,000
Interest Rate Contracts [Member] | Liability [Member] | Exchange Traded, Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	1,000,000
Derivative Liability, Net Fair Value	1,000,000
Derivative Liability, Net	1,000,000
Interest Rate Contracts [Member] | Liability [Member] | Over The Counter, Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	2,276,000,000
Derivative Liability, Fair Value Offset Amount	1,687,000,000
Derivative Liability, Cash Collateral	530,000,000
Derivative Liability, Net Fair Value	59,000,000
Derivative Liability, Net	59,000,000
Interest Rate Contracts [Member] | Assets [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value		4,918,000,000
Derivative Asset, Fair Value Offset Amount		1,981,000,000
Derivative Asset, Cash Collateral		458,000,000
Derivative Asset, Net Fair Value		2,479,000,000
Derivative Asset, Securities Collateral Held Under Master Netting Agreements		143,000,000
Derivative Asset, Net		2,336,000,000
Interest Rate Contracts [Member] | Assets [Member] | Exchange Cleared [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	1,003,000,000	807,000,000
Derivative Asset, Fair Value Offset Amount	779,000,000
Derivative Asset, Cash Collateral	195,000,000
Derivative Asset, Net Fair Value	29,000,000
Derivative Asset, Net	29,000,000
Interest Rate Contracts [Member] | Assets [Member] | Over The Counter [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	3,652,000,000
Derivative Asset, Fair Value Offset Amount	1,645,000,000
Derivative Asset, Cash Collateral	342,000,000
Derivative Asset, Net Fair Value	1,665,000,000
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	178,000,000
Derivative Asset, Net	1,487,000,000
Foreign Exchange [Member] | Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	204,000,000	241,000,000
Derivative Liability, Fair Value Offset Amount	85,000,000	80,000,000
Derivative Liability, Cash Collateral	20,000,000	20,000,000
Derivative Liability, Net Fair Value	99,000,000	141,000,000
Derivative Liability, Net	99,000,000	141,000,000
Foreign Exchange [Member] | Assets [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	284,000,000	314,000,000
Derivative Asset, Fair Value Offset Amount	129,000,000	159,000,000
Derivative Asset, Cash Collateral	13,000,000	47,000,000
Derivative Asset, Net Fair Value	142,000,000	108,000,000
Derivative Asset, Securities Collateral Held Under Master Netting Agreements	2,000,000	1,000,000
Derivative Asset, Net	140,000,000	107,000,000
Credit Risk Contract [Member] | Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	4,000,000	4,000,000
Derivative Liability, Fair Value Offset Amount	3,000,000	4,000,000
Derivative Liability, Cash Collateral	1,000,000
Credit Risk Contract [Member] | Assets [Member]
Offsetting Assets [Line Items]
Derivative Asset, Gross Fair Value	2,000,000	2,000,000
Derivative Asset, Fair Value Offset Amount	1,000,000	1,000,000
Derivative Asset, Cash Collateral	1,000,000	1,000,000
Other Contract [Member] | Liability [Member]
Offsetting Liabilities [Line Items]
Derivative Liability, Gross Fair Value	462,000,000	510,000,000
Derivative Liability, Net Fair Value	462,000,000	510,000,000
Derivative Liability, Net	$ 462,000,000	$ 510,000,000