Significant Accounting Policies - Additional Information (Detail) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2016 USD ($) segment $ / shares shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares
Significant Accounting Policies [Line Items]
Number of reportable segments | segment		4
Percentage of investment securities not classified as corporate securities, state and municipal securities, redeemable preferred stocks and U.S. government securities (less than)		1.00%
Fair value determined by third party		95.00%
Amortized cost		$ 14,188,050	$ 13,251,871
Fair Value		15,245,861	13,758,024
Advanced agent commissions receivable		353,000	334,000
Advertising costs charged to earnings and included in other operating expense		9,000	10,000	$ 8,000
Capitalized advertising costs		1,250,000	1,210,000
Carrying value of investment in low-income housing interests		280,000	306,000
Obligations under future commitments for low-income housing interests		57,000
Original cost of property and equipment		196,000	175,000
Accumulated depreciation		99,000	92,000
Depreciation expense		$ 9,800	8,000	7,400
Traditional life and health, interest rate, low end		2.50%
Traditional life and health, interest rate, high end		7.00%
Traditional life and health, weighted average interest rate		5.70%
Insurance policy charges		$ 18,300	$ 19,300	$ 20,900
Excess tax benefits		$ 27,867
Diluted weighted average shares outstanding | shares		122,367,785	126,757,235	132,640,244
Excess tax benefit from stock option exercises, financing activities	[1]	$ 0	$ 17,577	$ 18,524
Minimum | Equipment
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful life		3 years
Minimum | Building and Improvements
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful life		5 years
Maximum | Equipment
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful life		10 years
Maximum | Building and Improvements
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful life		40 years
Life insurance
Significant Accounting Policies [Line Items]
Proportion of future policy reserves which are not universal life type		86.00%
Equity Option | Minimum
Significant Accounting Policies [Line Items]
Option grants contractual term		7 years
Equity Option | Maximum
Significant Accounting Policies [Line Items]
Option grants contractual term		10 years
Employee | Equity Option | 5 Year Vesting Period | Torchmark Corporation 2011 Incentive Plan
Significant Accounting Policies [Line Items]
Option grants contractual term		10 years
Vesting period		5 years
Employee | Equity Option | 3 Year Vesting Period | Torchmark Corporation 2011 Incentive Plan
Significant Accounting Policies [Line Items]
Option grants contractual term		7 years
Vesting period		3 years
Director | Equity Option | Torchmark Corporation 2011 Incentive Plan
Significant Accounting Policies [Line Items]
Vesting period		6 months
Other assets
Significant Accounting Policies [Line Items]
Carrying value of investment in low-income housing interests		$ 280,000	302,000
Other long-term investments
Significant Accounting Policies [Line Items]
Carrying value of investment in low-income housing interests			4,000
Private placement fixed maturities
Significant Accounting Policies [Line Items]
Amortized cost		565,000	542,000
Fair Value		574,000	546,000
Fair Value, Inputs, Level 2
Significant Accounting Policies [Line Items]
Fair Value		14,577,456	13,124,523
Fair Value, Inputs, Level 2 | Private placement fixed maturities
Significant Accounting Policies [Line Items]
Fair Value		15,000	15,000
Fair Value, Inputs, Level 3
Significant Accounting Policies [Line Items]
Fair Value		623,103	601,188
Fair Value, Inputs, Level 3 | Private placement fixed maturities
Significant Accounting Policies [Line Items]
Fair Value		559,000	531,000
New Accounting Pronouncement, Early Adoption, Effect
Significant Accounting Policies [Line Items]
Excess tax benefits		$ 20,000
Diluted weighted average shares outstanding | shares		122,400,000
Increase in earnings per share as a result of the adoption (in dollars per share) | $ / shares		$ 0.13
Previous Accounting Guidance
Significant Accounting Policies [Line Items]
Excess tax benefits			$ 18,000	19,000
Diluted weighted average shares outstanding | shares			121,500,000
Excess tax benefit from stock option exercises, financing activities			$ 18,000	$ 19,000
Accounting Standards Update 2016-09
Significant Accounting Policies [Line Items]
Excess tax benefit from stock option exercises, operating activities		$ 20,000

[1] Certain current year amounts were prospectively adjusted to give effect to the adoption of ASU 2016-09 related to excess tax benefits from stock compensation as described in Note 1—Significant Accounting Policies under "Accounting Pronouncements Adopted in the Current Year."