Accumulated Other Comprehensive Income (Schedule of 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
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period			$ (119)
Net change in accumulated other comprehensive income (loss), net of tax	$ (29)	$ 9	212	$ 82
Accumulated other comprehensive income (loss), net of tax, balance at end of period	93		93
Unrealized Gains (Losses) on Available-for-Sale Investment Securities, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period	352	112	112	10
Net change in accumulated other comprehensive income (loss), net of tax	(32)	17	208	119
Accumulated other comprehensive income (loss), net of tax, balance at end of period	320	129	320	129
Gains (Losses) on Cash Flow Hedges, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period	(16)	(8)	(17)	22
Net change in accumulated other comprehensive income (loss), net of tax	3	(8)	4	(38)
Accumulated other comprehensive income (loss), net of tax, balance at end of period	(13)	(16)	(13)	(16)
Gains (Losses) on Pension Plan, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period	(214)	(187)	(214)	(188)
Net change in accumulated other comprehensive income (loss), net of tax	0	0	0	1
Accumulated other comprehensive income (loss), net of tax, balance at end of period	(214)	(187)	(214)	(187)
AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period	122	(83)	(119)	(156)
Net change in accumulated other comprehensive income (loss), net of tax	(29)	9	212	82
Accumulated other comprehensive income (loss), net of tax, balance at end of period	$ 93	$ (74)	$ 93	$ (74)