Investments - Schedule of Investment Funds (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2023	Dec. 31, 2022
Alternative Investment [Line Items]
Investment funds, unfunded commitments	$ 472,000
Investment funds
Alternative Investment [Line Items]
Investment funds, fair value	789,197	$ 768,689
Investment funds, unfunded commitments	471,690
Capital called from investment funds	21,000
Investment funds \| Commercial mortgage loans
Alternative Investment [Line Items]
Investment funds, fair value	454,144	431,405
Investment funds, unfunded commitments	330,245
Investment funds \| Opportunistic credit
Alternative Investment [Line Items]
Investment funds, fair value	157,899	158,524
Investment funds, unfunded commitments	$ 0
Investments, initial redemption, term	2 years
Investments, redemption, term	36 months
Investment funds \| Infrastructure
Alternative Investment [Line Items]
Investment funds, fair value	$ 158,036	159,534
Investment funds, unfunded commitments	21,366
Investment funds \| Other investments
Alternative Investment [Line Items]
Investment funds, fair value	19,118	$ 19,226
Investment funds, unfunded commitments	$ 120,079

Alternative Investment

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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 https://asc.fasb.org/extlink&oid=126976982&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 https://asc.fasb.org/extlink&oid=126972413&loc=SL7495116-110257

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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 https://asc.fasb.org/extlink&oid=126976982&loc=SL6742756-110258

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The cash outflow for securities or other assets acquired, which qualify for treatment as an investing activity and are to be liquidated, if necessary, beyond the current operating cycle. Includes cash flows from securities classified as trading securities that were acquired for reasons other than sale in the long-term.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3213-108585

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