Investments - Additional Information (Detail)	1 Months Ended	3 Months Ended	6 Months Ended		12 Months Ended
	Mar. 31, 2022 USD ($)	Jun. 30, 2022 USD ($) security	Jun. 30, 2022 USD ($) security	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Schedule of Debt and Equity Securities [Line Items]
Principal amount of bonds and certificates of deposit		$ 468,900,000	$ 468,900,000
Securities Exceeding 10% of Shareholders' Equity		0	0	$ 0	$ 0
Non-Income Producing Securities		0	0
Open reverse repurchase commitments		0	0	0	0
Securities Sold under Agreements to Repurchase		0	0	0	0
Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value, Downgraded in Period		18,300,000	18,300,000
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Downgraded in Period		2,100,000	2,100,000
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not Previously Recorded			0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss		$ 0	0	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Writeoff			$ 0	$ 0	$ 0
Percent Change in Investment Income		39.00%	24.00%
Proceeds from Debt, Net of Issuance Costs	$ 1,486,000,000
Percent Change in Book Yield		19.00%	7.00%
Corporate debt securities
Schedule of Debt and Equity Securities [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions Downgraded | security		2	2
Residential mortgage-backed securities
Schedule of Debt and Equity Securities [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions Downgraded | security		1	1