Business Segments - Liabilities by Segment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	$ 14,508,134	$ 13,953,826
Unearned and advance premiums	63,709	61,208
Policy claims and other benefits payable	365,402	350,826
Debt	1,647,726	1,665,033
Other	2,098,182	1,649,652
Total	18,683,153	17,680,545
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	2,098,182	1,649,652
Total	2,098,182	1,649,652
Life | Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	11,403,078	10,847,356
Unearned and advance premiums	17,701	17,850
Policy claims and other benefits payable	201,594	196,298
Debt	0	0
Other	0	0
Total	11,622,373	11,061,504
Health | Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	2,006,424	1,927,732
Unearned and advance premiums	46,008	43,358
Policy claims and other benefits payable	163,808	154,528
Debt	0	0
Other	0	0
Total	2,216,240	2,125,618
Annuity | Operating Segments
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	1,098,632	1,178,738
Unearned and advance premiums	0	0
Policy claims and other benefits payable	0	0
Debt	0	0
Other	0	0
Total	1,098,632	1,178,738
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	1,647,726	1,665,033
Other	0	0
Total	$ 1,647,726	$ 1,665,033