Reinsurance - GMIB Reinsurers (Details) - GMIB - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Ceded Credit Risk [Line Items]
GMIB recoverables	$ 926	$ 713
Berkshire
Ceded Credit Risk [Line Items]
GMIB recoverables	$ 429	332
Berkshire \| Secured \| GMIB Assets
Ceded Credit Risk [Line Items]
Concentration percentage	100.00%
Sun Life Assurance Company of Canada
Ceded Credit Risk [Line Items]
GMIB recoverables	$ 264	202
Liberty Re (Bermuda) Ltd.
Ceded Credit Risk [Line Items]
GMIB recoverables	$ 233	$ 179
Liberty Re (Bermuda) Ltd. \| Secured \| GMIB Assets
Ceded Credit Risk [Line Items]
Concentration percentage	73.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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