Accumulated Other Comprehensive Income (Schedule of Other Comprehensive Income Before Reclassifications and Amounts Reclassified from AOCI) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, before tax	$ (20)	$ 94	$ 317	$ 134
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, tax benefit (expense)	4	(23)	(77)	(32)
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, net of tax	(16)	71	240	102
Available-for-sale investment securities, net change, before tax	(20)	94	317	134
Available-for-sale investment securities, net change, tax benefit (expense)	4	(23)	(77)	(32)
Available-for-sale investment securities, net change, net of tax	(16)	71	240	102
Cash flow hedges, net unrealized gains (losses) arising during the period, before tax	0	(22)	(7)	(35)
Cash flow hedges, net unrealized gains (losses) arising during the period, tax benefit (expense)	1	6	3	9
Cash flow hedges, net unrealized gains (losses) arising during the period, net of tax	1	(16)	(4)	(26)
Cash flow hedges, amounts reclassified from AOCI, before tax	5	(2)	7	(5)
Cash flow hedges, amounts reclassified from AOCI, tax benefit (expense)	(2)	0	(2)	1
Cash flow hedges, amounts reclassified from AOCI, net of tax	3	(2)	5	(4)
Cash flow hedges, net change, before tax	5	(24)	0	(40)
Cash flow hedges, net change, tax benefit (expense)	(1)	6	1	10
Cash flow hedges, net change, net of tax	$ 4	$ (18)	$ 1	(30)
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