Schedule IV. Reinsurance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Life insurance in force, gross amount	$ 217,350,660	$ 203,894,460	$ 191,249,516
Life insurance in force, ceded to other companies	648,766	669,063	676,988
Life insurance in force, assumed from other companies	2,371,163	2,551,770	2,774,388
Life insurance in force, net amount	$ 219,073,057	$ 205,777,167	$ 193,346,916
Life insurance in force, percentage of amount assumed to net	1.10%	1.20%	1.40%
Premium, gross amount	$ 4,061,326	$ 3,787,025	$ 3,566,996
Premium, ceded to other companies	7,598	7,614	7,880
Premium, assumed from other companies	31,923	19,775	20,384
Premium, net amount	$ 4,085,651	$ 3,799,186	$ 3,579,500
Percentage of amount assumed to net	0.80%	0.50%	0.60%
Policy charges	$ 14,200	$ 14,700	$ 15,600
Life insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Premium, gross amount	2,868,759	2,642,555	2,486,127
Premium, ceded to other companies	4,286	4,241	4,357
Premium, assumed from other companies	19,502	19,775	20,384
Premium, net amount	$ 2,883,975	$ 2,658,089	$ 2,502,154
Percentage of amount assumed to net	0.70%	0.70%	0.80%
Health insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Premium, gross amount	$ 1,192,567	$ 1,144,470	$ 1,080,869
Premium, ceded to other companies	3,312	3,373	3,523
Premium, assumed from other companies	12,421	0	0
Premium, net amount	$ 1,201,676	$ 1,141,097	$ 1,077,346
Percentage of amount assumed to net	1.00%	0.00%	0.00%