Derivative And Credit-Related Financial Instruments (Schedule Of Derivative Instruments) (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	$ 20,051	$ 20,764
Fair Value of Gross Derivative Assets		407	818
Fair Value of Gross Derivative Liabilities		254	610
Derivative assets, Netting adjustment - Offsetting derivative liabilities		(84)	(127)
Derivative liabilities, Netting adjustment - Offsetting derivative assets		(84)	(127)
Derivative assets, Netting adjustment - Cash collateral received		(47)	(291)
Derivative liabilities, Netting adjustment - Cash collateral posted		(45)	(3)
Net derivative assets included in consolidated balance sheets	[2]	276	400
Net derivative liabilities included in the consolidated balance sheet	[2]	125	480
Derivative assets, securities pledged as collateral		(19)	(137)
Derivative liabilities, securities pledged as collateral		(8)	(3)
Net derivative assets after deducting amounts not offset in the consolidated balance sheets		257	263
Net derivative liabilities after deducting amounts not offset in the consolidated balance sheets		117	477
Credit valuation adjustments for counterparty credit risk		5	5
Risk management purposes
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	2,992	3,118
Fair Value of Gross Derivative Assets		94	150
Fair Value of Gross Derivative Liabilities		6	0
Risk management purposes | Derivatives designated as hedging instruments | Fair Value Hedging | Interest rate swap
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	2,275	2,525
Fair Value of Gross Derivative Assets		92	147
Fair Value of Gross Derivative Liabilities		4	0
Risk management purposes | Derivatives used as economic hedges | Foreign exchange spot, forwards and swaps
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	717	593
Fair Value of Gross Derivative Assets		2	3
Fair Value of Gross Derivative Liabilities		2	0
Customer-initiated and other activities
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	17,059	17,646
Fair Value of Gross Derivative Assets		313	668
Fair Value of Gross Derivative Liabilities		248	610
Customer-initiated and other activities | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	13,323	12,228
Fair Value of Gross Derivative Assets		131	139
Fair Value of Gross Derivative Liabilities		77	92
Customer-initiated and other activities | Interest rate caps and floors written
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	436	253
Fair Value of Gross Derivative Assets		0	0
Fair Value of Gross Derivative Liabilities		1	0
Customer-initiated and other activities | Interest rate caps and floors purchased
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	436	253
Fair Value of Gross Derivative Assets		1	0
Fair Value of Gross Derivative Liabilities		0	0
Customer-initiated and other activities | Interest rate swap
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	12,451	11,722
Fair Value of Gross Derivative Assets		130	139
Fair Value of Gross Derivative Liabilities		76	92
Customer-initiated and other activities | Energy contracts
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	2,227	3,127
Fair Value of Gross Derivative Assets		146	475
Fair Value of Gross Derivative Liabilities		144	472
Customer-initiated and other activities | Energy caps and floors written
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	419	536
Fair Value of Gross Derivative Assets		1	0
Fair Value of Gross Derivative Liabilities		31	85
Customer-initiated and other activities | Energy caps and floors purchased
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	419	536
Fair Value of Gross Derivative Assets		31	85
Fair Value of Gross Derivative Liabilities		1	0
Customer-initiated and other activities | Energy swaps
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	1,389	2,055
Fair Value of Gross Derivative Assets		114	390
Fair Value of Gross Derivative Liabilities		112	387
Customer-initiated and other activities | Foreign exchange spot, options and swaps
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	1,509	2,291
Fair Value of Gross Derivative Assets		36	54
Fair Value of Gross Derivative Liabilities		$ 27	$ 46

[1] Notional or contractual amounts, which represent the extent of involvement in the derivatives market, are used to determine the contractual cash flows required in accordance with the terms of the agreement. These amounts are typically not exchanged, significantly exceed amounts subject to credit or market risk and are not reflected in the consolidated balance sheets.

[2] Net derivative assets are included in “accrued income and other assets” and net derivative liabilities are included in “accrued expenses and other liabilities” on the consolidated balance sheets. Included in the fair value of net derivative assets and net derivative liabilities are credit valuation adjustments reflecting counterparty credit risk and credit risk of the Corporation. The fair value of net derivative assets included credit valuation adjustments for counterparty credit risk of $5 million at both December 31, 2016 and 2015.