Securities - Fair Value of Debt Securities AFS Contractual Maturity (Details) $ in Millions	Dec. 31, 2019 USD ($)
Securities available for sale
One Year or Less	$ 99
Over One Year Through Five Years	1,912
Over Five Years Through Ten Years	7,440
Over Ten Years	8,338
Total Fair Value	17,789
US Treasury and Government [Member]
Securities available for sale
One Year or Less	0
Over One Year Through Five Years	1,237
Over Five Years Through Ten Years	4,167
Over Ten Years	34
Total Fair Value	5,438
U.S. government agency and government-sponsored agencies
Securities available for sale
One Year or Less	0
Over One Year Through Five Years	167
Over Five Years Through Ten Years	1,021
Over Ten Years	4,280
Total Fair Value	5,468
Privately issued
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	762
Total Fair Value	762
Privately issued - commercial mortgage-backed securities
Securities available for sale
One Year or Less	32
Over One Year Through Five Years	0
Over Five Years Through Ten Years	1,356
Over Ten Years	2,101
Total Fair Value	3,489
Collateralized loan obligations
Securities available for sale
One Year or Less	0
Over One Year Through Five Years	0
Over Five Years Through Ten Years	430
Over Ten Years	1,061
Total Fair Value	1,491
Direct bank purchase bonds
Securities available for sale
One Year or Less	67
Over One Year Through Five Years	303
Over Five Years Through Ten Years	466
Over Ten Years	100
Total Fair Value	936
Other
Securities available for sale
One Year or Less	0
Over One Year Through Five Years	205
Over Five Years Through Ten Years	0
Over Ten Years	0
Total Fair Value	$ 205