Long-Term Debt and Shareholders' Equity (Changes In Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 8,033	$ 7,575	$ 7,886	$ 7,353
OCI (loss) before reclassifications, net of tax			(226)	313
Amounts reclassified from AOCI, net of tax			(35)	(24)
Other comprehensive income (loss)	(111)	(23)	(261)	289
Balance at end of period	7,774	7,668	7,774	7,668
Income tax (benefit) expense included in other comprehensive income (loss)			(85)	95
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	175	355	325	43
Balance at end of period	64	332	64	332
Net unrealized gains (losses) on investment securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			258	29
OCI (loss) before reclassifications, net of tax			(225)	228
Amounts reclassified from AOCI, net of tax			0	0
Other comprehensive income (loss)			(225)	228
Balance at end of period	33	257	33	257
Income tax (benefit) expense included in other comprehensive income (loss)			(73)	75
Net unrealized gains (losses) on derivatives and other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			69	28
OCI (loss) before reclassifications, net of tax			(1)	72
Amounts reclassified from AOCI, net of tax			(35)	(24)
Other comprehensive income (loss)			(36)	48
Balance at end of period	33	76	33	76
Income tax (benefit) expense included in other comprehensive income (loss)			(12)	16
Pension and post-retirement
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			(2)	(14)
OCI (loss) before reclassifications, net of tax			0	13
Amounts reclassified from AOCI, net of tax			0	0
Other comprehensive income (loss)			0	13
Balance at end of period	$ (2)	$ (1)	(2)	(1)
Income tax (benefit) expense included in other comprehensive income (loss)			$ 0	$ 4