Accumulated Other Comprehensive Income (Schedule of Changes in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 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	253	$ 20
Accumulated other comprehensive income (loss), net of tax, balance at end of period	134
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	112	10
Net change in accumulated other comprehensive income (loss), net of tax	256	31
Accumulated other comprehensive income (loss), net of tax, balance at end of period	368	41
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	(17)	22
Net change in accumulated other comprehensive income (loss), net of tax	(3)	(12)
Accumulated other comprehensive income (loss), net of tax, balance at end of period	(20)	10
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)	(188)
Net change in accumulated other comprehensive income (loss), net of tax	0	1
Accumulated other comprehensive income (loss), net of tax, balance at end of period	(214)	(187)
AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period	(119)	(156)
Net change in accumulated other comprehensive income (loss), net of tax	253	20
Accumulated other comprehensive income (loss), net of tax, balance at end of period	$ 134	$ (136)