Accumulated Other Comprehensive Income (Other Comprehensive Income (Loss) Reclassification Adjustments) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net holding gain (loss) on investment securities arising during the period, net of tax	$ 741	$ 237	$ 33	$ 586
Reclassification adjustment for net realized loss (gain) on investment securities, net of tax	(11)	1	8	9
Total reclassification adjustment on investments	730	238	41	595
Change in non-credit component of impairment losses on investments net of tax	10	(1)	(22)	(1)
Cash flow hedges, holding gain (loss), net of tax	3	0	6	3
Net change in unrecognized periodic benefit costs for defined benefit pension and postretirement benefit plans, net of tax	10	3	17	6
Foreign currency translation adjustment, net of tax	1	0	0	0
Net gain (loss) recognized in other comprehensive income, net of tax	$ 754	$ 240	$ 42	$ 603