Business Segments - Liabilities by Segment (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	$ 16,034,727	$ 15,243,536
Unearned and advance premiums	65,472	61,728
Policy claims and other benefits payable	412,940	399,507
Debt	2,026,138	1,922,804
Other	2,585,965	2,648,064
Total	21,125,242	20,275,639
Other
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	0	0
Unearned and advance premiums	0	0
Policy claims and other benefits payable	0	0
Debt	0	0
Other	2,585,965	2,648,064
Total	2,585,965	2,648,064
Life | Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	12,686,851	12,008,396
Unearned and advance premiums	19,874	18,968
Policy claims and other benefits payable	245,108	237,246
Debt	0	0
Other	0	0
Total	12,951,833	12,264,610
Health | Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	2,315,507	2,172,141
Unearned and advance premiums	45,598	42,760
Policy claims and other benefits payable	167,832	162,261
Debt	0	0
Other	0	0
Total	2,528,937	2,377,162
Annuity | Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	1,032,369	1,062,999
Unearned and advance premiums	0	0
Policy claims and other benefits payable	0	0
Debt	0	0
Other	0	0
Total	1,032,369	1,062,999
Investment | Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	0	0
Unearned and advance premiums	0	0
Policy claims and other benefits payable	0	0
Debt	2,026,138	1,922,804
Other	0	0
Total	$ 2,026,138	$ 1,922,804