Accumulated Other Comprehensive Income (Schedule of Changes in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 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	$ (12)	$ 53	241	$ 73
Accumulated other comprehensive income (loss), net of tax, balance at end of period	122		122
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	368	41	112	10
Net change in accumulated other comprehensive income (loss), net of tax	(16)	71	240	102
Accumulated other comprehensive income (loss), net of tax, balance at end of period	352	112	352	112
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	(20)	10	(17)	22
Net change in accumulated other comprehensive income (loss), net of tax	4	(18)	1	(30)
Accumulated other comprehensive income (loss), net of tax, balance at end of period	(16)	(8)	(16)	(8)
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	134	(136)	(119)	(156)
Net change in accumulated other comprehensive income (loss), net of tax	(12)	53	241	73
Accumulated other comprehensive income (loss), net of tax, balance at end of period	$ 122	$ (83)	$ 122	$ (83)