Schedule II - Condensed Financial Information of Registrant - Condensed Statements of Financial Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
ASSETS
Equity securities	$ 1,700,960	$ 1,530,228
Mortgage loans on real estate, net of allowance	5,097,017	5,124,707
Other invested assets	76,569	50,087
Deferred policy acquisition costs	1,423,007	1,497,261	$ 1,373,844	$ 1,294,443
Prepaid pension	78,990	57,117
Other assets	171,285	163,222
Separate account assets	1,073,891	918,369
Total assets	28,597,566	26,912,353	$ 26,386,764
LIABILITIES
Policyholders’ account balances	12,957,989	12,461,833
Other liabilities	446,882	452,985
Separate account liabilities	1,073,891	918,369
Total liabilities	22,601,803	21,640,838
EQUITY
Common stock	30,832	30,832
Additional paid-in capital	21,011	20,694
Accumulated other comprehensive income (loss)	99,518	(99,738)
Retained earnings	5,946,857	5,413,952
Treasury stock, at cost	(108,469)	(108,492)
Total equity	5,989,749	5,257,248
Total liabilities and equity	28,597,566	26,912,353
Parent Company
ASSETS
Fixed maturity securities	10,024,143	9,660,562
Equity securities	8,998	6,252
Mortgage loans on real estate, net of allowance	4,667,425	4,772,085
Other invested assets	1,305,533	1,487,383
Investment in subsidiaries	3,855,531	3,121,901
Deferred policy acquisition costs	1,159,812	1,224,752
Prepaid pension	78,990	57,117
Other assets	903,583	763,458
Separate account assets	1,073,891	918,369
Total assets	23,077,906	22,011,879
LIABILITIES
Policy liabilities	4,418,128	4,373,398
Policyholders’ account balances	11,076,418	10,943,189
Other liabilities	519,720	519,675
Separate account liabilities	1,073,891	918,369
Total liabilities	17,088,157	16,754,631
EQUITY
Common stock	30,832	30,832
Additional paid-in capital	21,011	20,694
Accumulated other comprehensive income (loss)	99,518	(99,738)
Retained earnings	5,946,857	5,413,952
Treasury stock, at cost	(108,469)	(108,492)
Total equity	5,989,749	5,257,248
Total liabilities and equity	$ 23,077,906	$ 22,011,879