Business Segments - Segment Premium Income by Distribution Channel and Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) segment	Mar. 31, 2020 USD ($)
Segment Reporting [Abstract]
Number of segments | segment	4
Segment Reporting Information [Line Items]
Revenue	$ 1,002,293	$ 929,835
% of Total	100.00%	100.00%
Life
Segment Reporting Information [Line Items]
Revenue	$ 708,119	$ 649,630
% of Total	100.00%	100.00%
Health
Segment Reporting Information [Line Items]
Revenue	$ 294,173	$ 280,205
% of Total	100.00%	100.00%
Annuity
Segment Reporting Information [Line Items]
Revenue	$ 1	$ 0
% of Total	100.00%	0.00%
American Income
Segment Reporting Information [Line Items]
Revenue	$ 362,246	$ 328,579
% of Total	36.00%	35.00%
American Income | Life
Segment Reporting Information [Line Items]
Revenue	$ 334,895	$ 302,852
% of Total	47.00%	47.00%
American Income | Health
Segment Reporting Information [Line Items]
Revenue	$ 27,351	$ 25,727
% of Total	9.00%	9.00%
American Income | Annuity
Segment Reporting Information [Line Items]
Revenue	$ 0	$ 0
% of Total	0.00%	0.00%
Direct to Consumer
Segment Reporting Information [Line Items]
Revenue	$ 263,388	$ 239,839
% of Total	26.00%	26.00%
Direct to Consumer | Life
Segment Reporting Information [Line Items]
Revenue	$ 244,028	$ 220,043
% of Total	35.00%	34.00%
Direct to Consumer | Health
Segment Reporting Information [Line Items]
Revenue	$ 19,360	$ 19,796
% of Total	7.00%	7.00%
Direct to Consumer | Annuity
Segment Reporting Information [Line Items]
Revenue	$ 0	$ 0
% of Total	0.00%	0.00%
Liberty National
Segment Reporting Information [Line Items]
Revenue	$ 122,777	$ 120,508
% of Total	12.00%	13.00%
Liberty National | Life
Segment Reporting Information [Line Items]
Revenue	$ 75,737	$ 72,868
% of Total	11.00%	11.00%
Liberty National | Health
Segment Reporting Information [Line Items]
Revenue	$ 47,040	$ 47,640
% of Total	16.00%	17.00%
Liberty National | Annuity
Segment Reporting Information [Line Items]
Revenue	$ 0	$ 0
% of Total	0.00%	0.00%
United American
Segment Reporting Information [Line Items]
Revenue	$ 119,365	$ 112,549
% of Total	12.00%	12.00%
United American | Life
Segment Reporting Information [Line Items]
Revenue	$ 2,277	$ 2,490
% of Total	0.00%	0.00%
United American | Health
Segment Reporting Information [Line Items]
Revenue	$ 117,087	$ 110,059
% of Total	40.00%	39.00%
United American | Annuity
Segment Reporting Information [Line Items]
Revenue	$ 1	$ 0
% of Total	100.00%	0.00%
Family Heritage
Segment Reporting Information [Line Items]
Revenue	$ 84,453	$ 78,004
% of Total	9.00%	8.00%
Family Heritage | Life
Segment Reporting Information [Line Items]
Revenue	$ 1,118	$ 1,021
% of Total	0.00%	0.00%
Family Heritage | Health
Segment Reporting Information [Line Items]
Revenue	$ 83,335	$ 76,983
% of Total	28.00%	28.00%
Family Heritage | Annuity
Segment Reporting Information [Line Items]
Revenue	$ 0	$ 0
% of Total	0.00%	0.00%
Other
Segment Reporting Information [Line Items]
Revenue	$ 50,064	$ 50,356
% of Total	5.00%	6.00%
Other | Life
Segment Reporting Information [Line Items]
Revenue	$ 50,064	$ 50,356
% of Total	7.00%	8.00%
Other | Health
Segment Reporting Information [Line Items]
Revenue	$ 0	$ 0
% of Total	0.00%	0.00%
Other | Annuity
Segment Reporting Information [Line Items]
Revenue	$ 0	$ 0
% of Total	0.00%	0.00%