Securities Financing Activities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Securities Financing Transaction [Line Items]
Reverse repurchase agreements	$ 0	$ 0
Securities borrowed	0	0
Total	0	0
Repurchase agreements	0	0
Total	0	0
Collateral
Securities Financing Transaction [Line Items]
Reverse repurchase agreements	(5)	0
Securities borrowed	0	(500)
Total	(5)	(500)
Repurchase agreements	(268)	(214)
Total	(268)	(214)
Federal Agency CMOs
Securities Financing Transaction [Line Items]
Assets pledged as collateral	307
Liabilities pledged as collateral	268
Gross Amount Presented in Balance Sheet
Securities Financing Transaction [Line Items]
Reverse repurchase agreements	18	6
Securities borrowed	0	500
Total	18	506
Repurchase agreements	281	220
Total	281	220
Netting Adjustments
Securities Financing Transaction [Line Items]
Reverse repurchase agreements	(13)	(6)
Securities borrowed	0	0
Total	(13)	(6)
Repurchase agreements	(13)	(6)
Total	$ (13)	$ (6)