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Commitments and Contingencies - Additional Information (Detail) $ in Millions		12 Months Ended
	Oct. 17, 2019 Officer	Dec. 31, 2019 USD ($) EquityFund	Dec. 31, 2018 USD ($)
Contingencies And Commitments [Line Items]
Number of private equity funds | EquityFund		2
Commitments towards private equity funds		$ 7.7
Commitments related to performance bonds		$ 9.3	$ 6.5
Commitments related to performance bonds expiration month and year		2024-08
Investment Commitments [Member]
Contingencies And Commitments [Line Items]
Aggregate investment committed in private equity funds		$ 7.9
Current Executive Officers [Member]
Contingencies And Commitments [Line Items]
Number of officers | Officer	2
Former Executive Officers [Member]
Contingencies And Commitments [Line Items]
Number of officers | Officer	1

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- Definition

Commitments related to performance bonds.

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- Definition

Commitments related to performance bonds expiration month and year.

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- Definition

Amount of contributions made that have been applied to private equity fund commitments.

+ References

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Contingencies and commitments.

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Number of officers.

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The number of investments in private equity funds.

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- Definition

Cost of the investment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=99383244&loc=d3e12121-115841

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