Reinsurance - Account Value, Net Amount at Risk and Contractholders for GMDB Business (Details) - Variable Annuity - GMDB contractholder in Thousands, $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2020 USD ($) contractholder	Dec. 31, 2019 USD ($) contractholder
Net Amount at Risk by Product and Guarantee [Line Items]
Account value	$ 8,650	$ 9,110
Net amount at risk	$ 1,694	$ 1,764
Number of contractholders (estimated) \| contractholder	190	200

Total number of underlying contractholders for the Guaranteed Minimum Death Benefit business.

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- Definition

Value of the general accounts corresponding to the specified product, guarantee type and subset of the guarantee.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Net amount at risk, representing the guaranteed benefit in excess of the current account balance corresponding to the specified product, guarantee type and subset of the guarantee.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 80
-Section 50
-Paragraph 1
-Subparagraph (d)(3),(5)
-URI http://asc.fasb.org/extlink&oid=121641442&loc=d3e19393-158473

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=121639652&loc=d3e7104-158389

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