Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) lease state guarantee	Dec. 31, 2018 USD ($)	Dec. 31, 2017	Apr. 02, 2019 USD ($)
Obligation with Joint and Several Liability Arrangement [Line Items]
Retention limits per life	$ 2,000,000
Life insurance ceded as percent of total life insurance in force	0.30%
Life and accident and health insurance ceded as a percent of premium income	0.20%
Life insurance assumed as a percent of life insurance in force	1.40%
Life and accident and health insurance assumed as a percent of premium income	0.60%	0.60%	0.70%
Number of guarantee agreements | guarantee	3
Guaranty liabilities	$ 0
Letters of credit outstanding	$ 150,000,000	$ 155,000,000		$ 150,000,000
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	$ 6,000,000