Debt - Short-term Borrowings (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Commercial mortgage backed securities
Short-term borrowings
FHLB advances, securities pledged as collateral	$ 1,200	$ 1,300
Residential mortgage backed securities
Short-term borrowings
FHLB advances, securities pledged as collateral	$ 581	$ 604
Federal Home Loan Bank borrowings \| Maximum
Short-term borrowings
Term	3 months	3 months

Amount of the collateral pledged in support of federal home loan bank advances outstanding.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123599511&loc=d3e64711-112823

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

Name:	us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant