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Components of Net Realized Investment Gains (Losses) (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Total net realized investment gains (losses)		$ (1,520)	$ (25,385)
Equity securities, Gross realized gains		627	1,806
Equity securities, Gross realized losses		(1,541)	(3,151)
Equity securities, Total net realized investment gains (losses)		(914)	(1,345)
Not Designated as Hedging Instrument | Interest Rate Swap
Schedule Of Available For Sale Securities [Line Items]
Gross realized gains		0	6,088
Gross realized losses		0	(1,364)
Total net realized investment gains (losses)	[1]	0	4,724
Fixed Income Securities
Schedule Of Available For Sale Securities [Line Items]
Gross realized gains		5	206
Gross realized losses		(611)	(28,970)
Total net realized investment gains (losses)		$ (606)	$ (28,764)
[1] Includes periodic net interest settlements related to the derivatives of $1.4 million for the quarter ended March 31, 2022.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=126980263&loc=SL75117546-209714

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