Accumulated Other Comprehensive Income (Schedule of Other Comprehensive Income Before Reclassifications and Amounts Reclassified from AOCI) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, before tax	$ 337	$ 40
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, tax benefit (expense)	(81)	(9)
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, net of tax	256	31
Available-for-sale investment securities, net change, before tax	337	40
Available-for-sale investment securities, net change, tax benefit (expense)	(81)	(9)
Available-for-sale investment securities, net change, net of tax	256	31
Cash flow hedges, net unrealized gains (losses) arising during the period, before tax	(7)	(13)
Cash flow hedges, net unrealized gains (losses) arising during the period, tax benefit (expense)	2	3
Cash flow hedges, net unrealized gains (losses) arising during the period, net of tax	(5)	(10)
Cash flow hedges, amounts reclassified from AOCI, before tax	2	(3)
Cash flow hedges, amounts reclassified from AOCI, tax benefit (expense)	0	1
Cash flow hedges, amounts reclassified from AOCI, net of tax	2	(2)
Cash flow hedges, net change, before tax	(5)	(16)
Cash flow hedges, net change, tax benefit (expense)	2	4
Cash flow hedges, net change, net of tax	$ (3)	(12)
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