Business Segments - Other Balances by Segment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	$ 13,953,826	$ 13,439,472
Unearned and advance premiums	61,208	61,430
Policy claims and other benefits payable	350,826	333,294
Debt	1,665,033	1,460,268
Other	1,649,652	1,949,100
Total	17,680,545	17,243,564
Life
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	10,847,356	10,353,286
Unearned and advance premiums	17,850	16,927
Policy claims and other benefits payable	196,298	186,429
Total	11,061,504	10,556,642
Health
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	1,927,732	1,831,338
Unearned and advance premiums	43,358	44,503
Policy claims and other benefits payable	154,528	146,865
Total	2,125,618	2,022,706
Annuity
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	1,178,738	1,254,848
Total	1,178,738	1,254,848
Investment
Segment Reporting, Other Significant Reconciling Item [Line Items]
Debt	1,665,033	1,460,268
Total	1,665,033	1,460,268
Other
Segment Reporting, Other Significant Reconciling Item [Line Items]
Other	1,649,652	1,949,100
Total	$ 1,649,652	$ 1,949,100