Investments - Securities Lending and Repurchase Agreements (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Securities Lending Transactions:
Gross amount of securities on loan	$ 0	$ 606
Gross amount of associated liability for collateral received	0	621
Repurchase agreements:
Securities for Reverse Repurchase Agreements	30	15
Gross amount of associated liability for collateral received, securities	$ 0	$ 34

Amount, before effects of master netting arrangements, of securities loaned to entities in exchange for collateral. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313

Name:	us-gaap_SecuritiesLoanedGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant