Securities - Fair Value of Debt Securities Available for Sale by Contractual Maturity (Details) $ in Millions	Sep. 30, 2020 USD ($)
Securities available for sale
One Year or Less	$ 103
Over One Year Through Five Years	779
Over Five Years Through Ten Years	7,234
Over Ten Years	8,554
Total Fair Value	16,670
U.S. Treasury and government agencies
Securities available for sale
One Year or Less	0
Over One Year Through Five Years	158
Over Five Years Through Ten Years	2,963
Over Ten Years	161
Total Fair Value	3,282
U.S. government agency and government-sponsored agencies - residential mortgage-backed securities
Securities available for sale
One Year or Less	0
Over One Year Through Five Years	66
Over Five Years Through Ten Years	1,017
Over Ten Years	4,378
Total Fair Value	5,461
Residential - non-agency
Securities available for sale
One Year or Less	0
Over One Year Through Five Years	0
Over Five Years Through Ten Years	0
Over Ten Years	655
Total Fair Value	655
Commercial - non-agency
Securities available for sale
One Year or Less	0
Over One Year Through Five Years	0
Over Five Years Through Ten Years	1,779
Over Ten Years	2,647
Total Fair Value	4,426
Collateralized loan obligations
Securities available for sale
One Year or Less	0
Over One Year Through Five Years	7
Over Five Years Through Ten Years	731
Over Ten Years	633
Total Fair Value	1,371
Direct bank purchase bonds
Securities available for sale
One Year or Less	94
Over One Year Through Five Years	369
Over Five Years Through Ten Years	394
Over Ten Years	80
Total Fair Value	937
Other
Securities available for sale
One Year or Less	9
Over One Year Through Five Years	179
Over Five Years Through Ten Years	350
Over Ten Years	0
Total Fair Value	$ 538

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