Investments - Additional Information (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2021 USD ($) loan	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Securities, Available-for-sale [Line Items]
Allowance for credit losses	$ 827	$ 3,505
Increase (decrease) in allowance	(2,700)
Commercial mortgage participations
Debt Securities, Available-for-sale [Line Items]
Carrying value, net of valuation allowance	$ 141,843	160,602
Number of loans \| loan	22
Allowance for credit losses	$ 827	$ 3,505	$ 0

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Name:	us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant