Fair Value Measurements - Company's Portfolio of Other Investments Measured Using Net Asset Valuations (Details) - Fair Value Measured at Net Asset Value Per Share - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 1,086,706,000	$ 725,803,000
Unfunded Commitments	1,207,457,000	1,327,137,000
Private credit funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	771,383,000	473,112,000
Unfunded Commitments	714,302,000	868,571,000
Private equity funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	315,323,000	241,297,000
Unfunded Commitments	493,155,000	458,566,000
Hedge funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 0	11,394,000
Unfunded Commitments		$ 0

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.

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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- 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

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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