Investments - Schedule of Investment Funds (Details) - Investment funds - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Investment [Line Items]
Investment funds, fair value	$ 185,851	$ 108,241
Investment funds, unfunded commitments	550,000
Commercial mortgage loans, not redeemable
Investment [Line Items]
Investment funds, fair value	26,145	0
Investment funds, unfunded commitments	225,000
Commercial mortgage loans, redeemable
Investment [Line Items]
Investment funds, fair value	0	0
Investment funds, unfunded commitments	$ 250,000
Redemption period	6 months
Commercial mortgage loans
Investment [Line Items]
Investment funds, fair value	$ 26,145	0
Investment funds, unfunded commitments	$ 475,000
Expected life of investment	7 years
Opportunistic credit
Investment [Line Items]
Investment funds, fair value	$ 159,399	108,241
Investment funds, unfunded commitments	$ 0
Redemption period	36 months
Initial lock period	2 years
Infrastructure equity
Investment [Line Items]
Investment funds, fair value	$ 307	$ 0
Investment funds, unfunded commitments	$ 75,000
Expected life of investment	10 years

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

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Fair Value, Investments, Entities That Calculate Net Asset Value Per Share, Redemption Restriction, Initial Lock Period In Effect

+ 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=117815213&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=117332851&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 http://asc.fasb.org/extlink&oid=117815213&loc=SL6742756-110258

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