Accumulated Other Comprehensive Income (Schedule of Other Comprehensive Income Before Reclassifications and Amounts Reclassified from AOCI) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, before tax	$ (42)	$ 24	$ 275	$ 158
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, tax benefit (expense)	10	(7)	(67)	(39)
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, net of tax	(32)	17	208	119
Available-for-sale investment securities, net change, before tax	(42)	24	275	158
Available-for-sale investment securities, net change, tax benefit (expense)	10	(7)	(67)	(39)
Available-for-sale investment securities, net change, net of tax	(32)	17	208	119
Cash flow hedges, net unrealized gains (losses) arising during the period, before tax	0	(9)	(7)	(44)
Cash flow hedges, net unrealized gains (losses) arising during the period, tax benefit (expense)	0	2	3	11
Cash flow hedges, net unrealized gains (losses) arising during the period, net of tax	0	(7)	(4)	(33)
Cash flow hedges, amounts reclassified from AOCI, before tax	4	(2)	11	(7)
Cash flow hedges, amounts reclassified from AOCI, tax benefit (expense)	(1)	1	(3)	2
Cash flow hedges, amounts reclassified from AOCI, net of tax	3	(1)	8	(5)
Cash flow hedges, net change, before tax	4	(11)	4	(51)
Cash flow hedges, net change, tax benefit (expense)	(1)	3	0	13
Cash flow hedges, net change, net of tax	$ 3	$ (8)	$ 4	(38)
Pension plan, unrealized gains (losses) arising during the period, before tax				1
Pension plan, unrealized gains (losses) arising during the period, tax benefit (expense)				0
Pension plan, unrealized gains (losses) arising during the period, net of tax				1
Pension plan, net change, before tax				1
Pension plan, net change, tax benefit (expense)				0
Pension plan, net change, net of tax				$ 1