Fair Value Measurements (Assets And Liabilities Recorded At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		$ 15,028	$ 12,398
Derivative assets		700	317
Derivative liabilities		229	141
U.S. Treasury and other U.S. government agency securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		4,658	2,792
Residential mortgage-backed securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale	[1]	10,370	9,606
Recurring
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		15,028	12,398
Derivative assets		700	317
Total assets at fair value		15,895	12,864
Derivative liabilities		229	141
Deferred compensation plan liabilities		107	95
Total liabilities at fair value		336	236
Recurring | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		4,658	2,792
Derivative assets		0	0
Total assets at fair value		4,825	2,941
Derivative liabilities		0	0
Deferred compensation plan liabilities		107	95
Total liabilities at fair value		107	95
Recurring | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		10,370	9,606
Derivative assets		661	295
Total assets at fair value		11,031	9,901
Derivative liabilities		229	141
Deferred compensation plan liabilities		0	0
Total liabilities at fair value		229	141
Recurring | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		0	0
Derivative assets		39	22
Total assets at fair value		39	22
Derivative liabilities		0	0
Deferred compensation plan liabilities		0	0
Total liabilities at fair value		0	0
Recurring | Interest rate contracts
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		531	211
Derivative liabilities		61	39
Recurring | Interest rate contracts | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0	0
Derivative liabilities		0	0
Recurring | Interest rate contracts | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		492	189
Derivative liabilities		61	39
Recurring | Interest rate contracts | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		39	22
Derivative liabilities		0	0
Recurring | Energy derivative contracts
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		151	96
Derivative liabilities		149	92
Recurring | Energy derivative contracts | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0	0
Derivative liabilities		0	0
Recurring | Energy derivative contracts | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		151	96
Derivative liabilities		149	92
Recurring | Energy derivative contracts | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0	0
Derivative liabilities		0	0
Recurring | Foreign exchange contracts
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		18	10
Derivative liabilities		19	10
Recurring | Foreign exchange contracts | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0	0
Derivative liabilities		0	0
Recurring | Foreign exchange contracts | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		18	10
Derivative liabilities		19	10
Recurring | Foreign exchange contracts | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Derivative assets		0	0
Derivative liabilities		0	0
Recurring | Deferred compensation plan assets
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		107	95
Recurring | Deferred compensation plan assets | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		107	95
Recurring | Deferred compensation plan assets | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		0	0
Recurring | Deferred compensation plan assets | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Trading securities		0	0
Recurring | Equity and other non-debt securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Other equity securities		60	54
Recurring | Equity and other non-debt securities | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Other equity securities		60	54
Recurring | Equity and other non-debt securities | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Other equity securities		0	0
Recurring | Equity and other non-debt securities | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Other equity securities		0	0
Recurring | U.S. Treasury and other U.S. government agency securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		4,658	2,792
Recurring | U.S. Treasury and other U.S. government agency securities | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		4,658	2,792
Recurring | U.S. Treasury and other U.S. government agency securities | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		0	0
Recurring | U.S. Treasury and other U.S. government agency securities | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale		0	0
Recurring | Residential mortgage-backed securities
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale	[1]	10,370	9,606
Recurring | Residential mortgage-backed securities | Level 1
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale	[1]	0	0
Recurring | Residential mortgage-backed securities | Level 2
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale	[1]	10,370	9,606
Recurring | Residential mortgage-backed securities | Level 3
Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Investment securities available-for-sale	[1]	$ 0	$ 0

[1] Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.