Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Income (Loss) Reclassification Adjustments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net holding gain (loss) on investment securities arising during the period, net of tax	$ 695	$ (465)	$ 280
Reclassification adjustment for net realized loss (gain) on investment securities, net of tax	(15)	47	(107)
Total reclassification adjustments on investments	680	(418)	173
Non-credit component of other-than-temporary impairments on investments, net of tax	0	(2)	4
Cash flow hedges, holding (loss) gain, net of tax	(16)	37	(65)
Net change in unrecognized periodic benefit costs for defined benefit pension and postretirement benefit plans, net of tax	26	(90)	51
Foreign currency translation adjustment, net of tax	0	(1)	3
Net gain (loss) recognized in other comprehensive loss, net of tax	$ 690	$ (474)	$ 166