Variable Interest Entities - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Variable Interest Entity
Assets	$ 206,899		$ 204,680
Lower limit
Variable Interest Entity
Unfunded commitments, year expected to be funded	2021
Upper limit
Variable Interest Entity
Unfunded commitments, year expected to be funded	2036
Variable Interest Entity, Not Primary Beneficiary | Loans provided to VIEs
Variable Interest Entity
Unfunded commitment amounts	$ 1,400		1,200
Variable Interest Entity, Not Primary Beneficiary | CDC investments
Variable Interest Entity
Assets	1,546		1,546
Variable Interest Entity, Not Primary Beneficiary | CDC investments | Qualified Affordable Housing Tax Credits
Variable Interest Entity
Assets	1,300		1,300
Unfunded commitments in qualifying LIHTC investments	431		478
Variable Interest Entity, Not Primary Beneficiary | Private equity investments
Variable Interest Entity
Assets	104		117
Unfunded commitment amounts	94		$ 83
Capital contribution to private equity investments	$ 2	$ 5