Long-Term Debt and Shareholders' Equity (Changes In Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 7,933	$ 7,472	$ 7,886	$ 7,353
OCI (loss) before reclassifications, net of tax			(127)	325
Amounts reclassified from AOCI, net of tax			(23)	(13)
Other comprehensive income (loss)	27	96	(150)	312
Balance at end of period	8,033	7,575	8,033	7,575
Income tax (benefit) expense included in other comprehensive income (loss)			(48)	102
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	148	259	325	43
Balance at end of period	175	355	175	355
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			(130)	241
Amounts reclassified from AOCI, net of tax			0	0
Other comprehensive income (loss)			(130)	241
Balance at end of period	128	270	128	270
Income tax (benefit) expense included in other comprehensive income (loss)			(42)	79
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			3	71
Amounts reclassified from AOCI, net of tax			(23)	(13)
Other comprehensive income (loss)			(20)	58
Balance at end of period	49	86	49	86
Income tax (benefit) expense included in other comprehensive income (loss)			(6)	19
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