Stock-Based Compensation - Analysis of Shares Available for Grant (Detail)	12 Months Ended
	Dec. 31, 2015 shares	Dec. 31, 2014 shares	Dec. 31, 2013 shares
Activity by Share-based Payment Award
Balance at January 1	8,458,593	4,368,753	6,804,452
Options expired and forfeited during year	90,371	3,488	128,109
Restricted stock expired and forfeited during year (counted as 3.1 options)	89,745	31,620	9,625
Balance at December 31	6,872,282	8,458,593	4,368,753
Stock Options [Member]
Activity by Share-based Payment Award
Options granted during year	(1,334,514)	(1,523,982)	(1,626,863)
2011 Plan Amendment [Member]
Activity by Share-based Payment Award
Balance at January 1	6,300,000.0
2011 Plan amendment	0	6,300,000	0
Balance at December 31		6,300,000.0
Torchmark Corporation 2011 Incentive Plan [Member] | Restricted Stock, Restricted Stock Units And Performance Shares [Member]
Activity by Share-based Payment Award
Restricted stock, restricted stock units, and performance shares granted under the Torchmark Corporation 2011 Incentive Plan (counted as 3.1 options per grant)	(431,913)	(721,286)	(946,570)
Minimum [Member]
Activity by Share-based Payment Award
Ratio by which each grant of restricted stock reduces shares available for options	3.1
Ratio by which each grant of stock options reduces shares available for grant	0.85
Maximum [Member]
Activity by Share-based Payment Award
Ratio by which each grant of restricted stock reduces shares available for options	3.88
Ratio by which each grant of stock options reduces shares available for grant	1