Investments - Schedule of Investment Funds (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Alternative Investment [Line Items]
Investment funds, unfunded commitments	$ 357,000
Investment funds
Alternative Investment [Line Items]
Investment funds, fair value	586,223	$ 385,038
Investment funds, unfunded commitments	357,013
Investment funds \| Commercial mortgage loans
Alternative Investment [Line Items]
Investment funds, fair value	397,723	227,050
Investment funds, unfunded commitments	$ 124,913
Redemption period	6 months
Expected life of investment	7 years
Investment funds \| Opportunistic credit
Alternative Investment [Line Items]
Investment funds, fair value	$ 170,117	157,461
Investment funds, unfunded commitments	$ 0
Redemption period	36 months
Initial lock period	2 years
Investment funds \| Other investments
Alternative Investment [Line Items]
Investment funds, fair value	$ 18,383	$ 527
Investment funds, unfunded commitments	$ 232,100

Alternative Investment

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- Definition

Fair Value, Investments, Entities that Calculate Net Asset Value, Investment Term

+ References

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+ References

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Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=SL6742756-110258

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 35
-Paragraph 54B
-URI http://asc.fasb.org/extlink&oid=122636397&loc=SL7495116-110257

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Period when redemption restriction has been in effect for investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure), in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 6A
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=SL6742756-110258

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