Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2021 USD ($) state guarantee lease	Dec. 31, 2020 USD ($)	Dec. 31, 2019	Oct. 26, 2021 USD ($)	Oct. 25, 2021 USD ($)
Obligation with Joint and Several Liability Arrangement [Line Items]
Retention limits per life	$ 500,000
Life insurance ceded as percent of total life insurance in force	0.30%	0.30%
Life and accident and health insurance ceded as a percent of premium income	0.20%	0.20%
Life insurance assumed as a percent of life insurance in force	1.10%	1.20%
Life and accident and health insurance assumed as a percent of premium income	0.80%	0.50%	0.60%
Number of guarantee agreements | guarantee	3
Guaranty liabilities	$ 0
Letters of credit outstanding	$ 125,000,000	$ 135,000,000		$ 135,000,000	$ 125,000,000
Number of states private entities contracted with for audits | state	47
Letter of Credit
Obligation with Joint and Several Liability Arrangement [Line Items]
Letter of credit maximum available amount	$ 250,000,000
Equipment Lease Guarantees
Obligation with Joint and Several Liability Arrangement [Line Items]
Number of guaranteed leasing agreements | lease	2
Remaining undiscounted payments under guaranteed lease agreements	$ 3,000,000