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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 7,575	$ 7,599	$ 7,353	$ 7,578
OCI before reclassifications, net of tax			313	296
Amounts reclassified from AOCI, net of tax			(24)	3
Other comprehensive income (loss)	(23)	23	289	299
Balance at end of period	7,668	7,509	7,668	7,509
Income tax expense included in OCI			95	98
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	355	25	43	(250)
Balance at end of period	332	49	332	49
Net unrealized gains (losses) on investment securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			29	(228)
OCI before reclassifications, net of tax			228	257
Amounts reclassified from AOCI, net of tax			0	0
Other comprehensive income (loss)			228	257
Balance at end of period	257	29	257	29
Income tax expense included in OCI			75	84
Net unrealized gains (losses) on derivatives and other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			28	(1)
OCI before reclassifications, net of tax			72	39
Amounts reclassified from AOCI, net of tax			(24)	3
Other comprehensive income (loss)			48	42
Balance at end of period	76	41	76	41
Income tax expense included in OCI			16	14
Pension and post-retirement [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period			(14)	(21)
OCI before reclassifications, net of tax			13	0
Amounts reclassified from AOCI, net of tax			0	0
Other comprehensive income (loss)			13	0
Balance at end of period	$ (1)	$ (21)	(1)	(21)
Income tax expense included in OCI			$ 4	$ 0