Derivative And Credit-Related Financial Instruments (Schedule Of Derivative Instruments) (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	$ 20,545	$ 20,051
Fair Value of Gross Derivative Assets		192	407
Fair Value of Gross Derivative Liabilities		190	254
Derivative assets, Netting adjustment - Offsetting derivative liabilities		(49)	(84)
Derivative liabilities, Netting adjustment - Offsetting derivative assets		(49)	(84)
Derivative assets, Netting adjustment - Cash collateral received		(1)	(47)
Derivative liabilities, Netting adjustment - Cash collateral posted		(39)	(45)
Net derivative assets included in consolidated balance sheets	[2]	142	276
Net derivative liabilities included in the consolidated balance sheet	[2]	102	125
Derivative assets, securities pledged as collateral		(3)	(19)
Derivative liabilities, securities pledged as collateral		(24)	(8)
Net derivative assets after deducting amounts not offset in the consolidated balance sheets		139	257
Net derivative liabilities after deducting amounts not offset in the consolidated balance sheets		78	117
Credit valuation adjustments for counterparty credit risk		4	5
Risk management purposes
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	2,425	2,992
Fair Value of Gross Derivative Assets		0	94
Fair Value of Gross Derivative Liabilities		4	6
Risk management purposes | Derivatives designated as hedging instruments | Fair Value Hedging | Interest rate swap
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1],[3]	1,775	2,275
Fair Value of Gross Derivative Assets	[3]	0	92
Fair Value of Gross Derivative Liabilities	[3]	2	4
Risk management purposes | Derivatives used as economic hedges | Foreign exchange spot, forwards and swaps
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	650	717
Fair Value of Gross Derivative Assets		0	2
Fair Value of Gross Derivative Liabilities		2	2
Customer-initiated and other activities
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	18,120	17,059
Fair Value of Gross Derivative Assets		192	313
Fair Value of Gross Derivative Liabilities		186	248
Customer-initiated and other activities | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	14,389	13,323
Fair Value of Gross Derivative Assets		57	131
Fair Value of Gross Derivative Liabilities		57	77
Customer-initiated and other activities | Interest rate caps and floors written
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	635	436
Fair Value of Gross Derivative Assets		0	0
Fair Value of Gross Derivative Liabilities		0	1
Customer-initiated and other activities | Interest rate caps and floors purchased
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	635	436
Fair Value of Gross Derivative Assets		0	1
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],[3]	13,119	12,451
Fair Value of Gross Derivative Assets	[3]	57	130
Fair Value of Gross Derivative Liabilities	[3]	57	76
Customer-initiated and other activities | Energy contracts
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	1,847	2,227
Fair Value of Gross Derivative Assets		93	146
Fair Value of Gross Derivative Liabilities		91	144
Customer-initiated and other activities | Energy caps and floors written
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	164	419
Fair Value of Gross Derivative Assets		0	1
Fair Value of Gross Derivative Liabilities		11	31
Customer-initiated and other activities | Energy caps and floors purchased
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	164	419
Fair Value of Gross Derivative Assets		11	31
Fair Value of Gross Derivative Liabilities		0	1
Customer-initiated and other activities | Energy swaps
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	1,519	1,389
Fair Value of Gross Derivative Assets		82	114
Fair Value of Gross Derivative Liabilities		80	112
Customer-initiated and other activities | Foreign exchange spot, options and swaps
Derivatives, Fair Value [Line Items]
Notional/Contract Amount	[1]	1,884	1,509
Fair Value of Gross Derivative Assets		42	36
Fair Value of Gross Derivative Liabilities		$ 38	$ 27

[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 $4 million and $5 million at December 31, 2017 and 2016, respectively.

[3] Due to clearinghouse rule changes, beginning January 1, 2017, variation margin payments are treated as settlements of derivative exposure rather than as collateral. As a result, these payments are now considered in determining the fair value of centrally cleared derivatives, resulting in centrally cleared derivatives having a fair value of approximately zero.