Securities Financing Activities - Summarized Securities Financing Agreements (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Securities Financing Transaction [Line Items]
Reverse repurchase agreements	$ 0	$ 0
Total	0	0
Repurchase agreements	0	0
Total	0	0
Collateral
Securities Financing Transaction [Line Items]
Reverse repurchase agreements	(3)	0
Total	(3)	0
Repurchase agreements	(261)	(180)
Total	(261)	(180)
Federal Agency CMOs
Securities Financing Transaction [Line Items]
Assets pledged as collateral	396
Liabilities pledged as collateral	260
Gross Amount Presented in Balance Sheet
Securities Financing Transaction [Line Items]
Reverse repurchase agreements	9	5
Total	9	5
Repurchase agreements	267	187
Total	267	187
Netting Adjustments
Securities Financing Transaction [Line Items]
Reverse repurchase agreements	(6)	(5)
Total	(6)	(5)
Repurchase agreements	(6)	(7)
Total	$ (6)	$ (7)