Fair Value (Schedule Of Key Model Inputs And Assumptions Used To Fair Value Certain Asset-Backed Securities) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Trading Securities	$ 40	$ 115
Other Assets, Fair Value Disclosure	95	91
Other Liabilities, Fair Value Disclosure	95	91
Estimate of Fair Value Measurement [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	15,606	13,372
Trading Securities	40	115
Assets, Fair Value Disclosure	16,408	14,250
Financial Instruments Sold, Not yet Purchased, at Fair Value	133	25
Financial and Nonfinancial Liabilities, Fair Value Disclosure	284	175
Estimate of Fair Value Measurement [Member] | Derivative [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	55	64
Other Liabilities, Fair Value Disclosure	56	59
Interest Rate Contract [Member] | Derivative [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	2	4
Other Liabilities, Fair Value Disclosure	4	1
Fair Value, Inputs, Level 3 [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Assets, Fair Value Disclosure	98	93
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Assets, Fair Value Disclosure	16,058	13,853
Financial and Nonfinancial Liabilities, Fair Value Disclosure	49	50
Fair Value, Inputs, Level 1 [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Assets, Fair Value Disclosure	252	304
Financial and Nonfinancial Liabilities, Fair Value Disclosure	235	125
Foreign Exchange Contract [Member] | Derivative [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	9	11
Other Liabilities, Fair Value Disclosure	7	9
Interest Rate Swap [Member] | Derivative [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	44	49
Other Liabilities, Fair Value Disclosure	45	49
Interest-Only-Strip [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	20	20
Private Equity Funds [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Noninterest Bearing Investments Fair Value Disclosure	93	91
Bank-owned life insurance [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Noninterest Bearing Investments Fair Value Disclosure	499	497
Mutual Funds And Stock Equity Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	134	185
Debt Securities [Member] | Available-for-sale Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	24
Other Credit Derivatives [Member] | Asset-Backed Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure		24
US States and Political Subdivisions Debt Securities [Member] | Available-for-sale Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	1,285	1,154
US Government Corporations and Agencies Securities [Member] | Available-for-sale Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	14,163	12,009
Fair Value, Inputs, Level 2 [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	15,473	13,188
Trading Securities	40	115
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Inputs, Level 2 [Member] | Derivative [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	46	53
Other Liabilities, Fair Value Disclosure	49	50
Fair Value, Inputs, Level 2 [Member] | Interest Rate Contract [Member] | Derivative [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	2	4
Other Liabilities, Fair Value Disclosure	4	1
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member] | Derivative [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	44	49
Other Liabilities, Fair Value Disclosure	45	49
Fair Value, Inputs, Level 2 [Member] | Private Equity Funds [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Noninterest Bearing Investments Fair Value Disclosure
Fair Value, Inputs, Level 2 [Member] | Bank-owned life insurance [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Noninterest Bearing Investments Fair Value Disclosure	499	497
Fair Value, Inputs, Level 2 [Member] | Mutual Funds And Stock Equity Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	1	1
Fair Value, Inputs, Level 2 [Member] | Debt Securities [Member] | Available-for-sale Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	24
Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member] | Available-for-sale Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	1,285	1,154
Fair Value, Inputs, Level 2 [Member] | US Government Corporations and Agencies Securities [Member] | Available-for-sale Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	14,163	12,009
Fair Value, Inputs, Level 2 [Member] | Other (Including ABS CDOs) [Member] | Asset-Backed Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure		24
Fair Value, Inputs, Level 3 [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	0	0
Financial Instruments Sold, Not yet Purchased, at Fair Value	0	0
Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	0	0
Other Liabilities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Interest-Only-Strip [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	20	20
Fair Value, Inputs, Level 3 [Member] | Private Equity Funds [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Noninterest Bearing Investments Fair Value Disclosure	78	73
Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member] | Available-for-sale Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure
Fair Value, Inputs, Level 3 [Member] | US Government Corporations and Agencies Securities [Member] | Available-for-sale Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Other (Including ABS CDOs) [Member] | Asset-Backed Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure
Fair Value, Inputs, Level 1 [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	133	184
Other Assets, Fair Value Disclosure	95	91
Financial Instruments Sold, Not yet Purchased, at Fair Value	133	25
Other Liabilities, Fair Value Disclosure	95	91
Fair Value, Inputs, Level 1 [Member] | Derivative [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	9	11
Other Liabilities, Fair Value Disclosure	7	9
Fair Value, Inputs, Level 1 [Member] | Foreign Exchange Contract [Member] | Derivative [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Assets, Fair Value Disclosure	9	11
Other Liabilities, Fair Value Disclosure	7	9
Fair Value, Inputs, Level 1 [Member] | Private Equity Funds [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Other Noninterest Bearing Investments Fair Value Disclosure	15	18
Fair Value, Inputs, Level 1 [Member] | Mutual Funds And Stock Equity Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	133	184
Fair Value, Inputs, Level 1 [Member] | US Government Corporations and Agencies Securities [Member] | Available-for-sale Securities [Member]
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Investments, Fair Value Disclosure	$ 0	$ 0