Globe Life (GL) 10-K 27 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 16, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	TMK
Entity Registrant Name	TORCHMARK CORP
Entity Central Index Key	320,335
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		114,081,876
Entity Public Float			$ 8,893,792,769

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets:
Fixed maturities-available for sale, at fair value (amortized cost: 2017—$14,995,101; 2016—$14,188,050)	$ 16,969,325	$ 15,245,861
Policy loans	529,529	507,975
Other long-term investments	108,559	53,852
Short-term investments	127,071	72,040
Total investments	17,734,484	15,879,728
Cash	118,563	76,163
Accrued investment income	233,453	223,148
Other receivables	391,775	384,454
Deferred acquisition costs	3,958,063	3,783,158
Goodwill	441,591	441,591
Other assets	528,536	520,313
Assets related to discontinued operations	68,520	127,532
Total assets	23,474,985	21,436,087
Liabilities:
Future policy benefits	13,439,472	12,825,837
Unearned and advance premiums	61,430	64,017
Policy claims and other benefits payable	333,294	299,565
Other policyholders' funds	97,635	96,993
Total policy liabilities	13,931,831	13,286,412
Current and deferred income taxes payable	1,312,002	1,743,990
Other liabilities	489,609	413,760
Short-term debt	328,067	264,475
Long-term debt (estimated fair value: 2017—$1,228,392; 2016—$1,233,019)	1,132,201	1,133,165
Liabilities related to discontinued operations	49,854	27,424
Total liabilities	17,243,564	16,869,226
Commitments and Contingencies (Note 15)
Shareholders' equity:
Preferred stock, par value $1 per share—Authorized 5,000,000 shares; outstanding: 0 in 2017 and 2016	0	0
Common stock, par value $1 per share—Authorized 320,000,000 shares; outstanding: (2017—124,218,183 issued, less 9,625,104 held in treasury and 2016—127,218,183 issued, less 9,187,075 held in treasury)	124,218	127,218
Additional paid-in capital	508,476	490,421
Accumulated other comprehensive income (loss)	1,424,274	577,574
Retained earnings	4,806,208	3,890,798
Treasury stock	(631,755)	(519,150)
Total shareholders’ equity	6,231,421	4,566,861
Total liabilities and shareholders’ equity	$ 23,474,985	$ 21,436,087

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Fixed maturities, available for sale, amortized cost	$ 14,995,101	$ 14,188,050
Long-term debt, fair value	$ 1,228,392	$ 1,233,019
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized	320,000,000	320,000,000
Common stock, shares issued	124,218,183	127,218,183
Common stock, shares held in treasury	9,625,104	9,187,075

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Life premium	$ 2,306,547	$ 2,189,333	$ 2,073,065
Health premium	976,373	947,663	925,520
Other premium	15	38	135
Total premium	3,282,935	3,137,034	2,998,720
Net investment income	847,885	806,903	773,951
Realized investment gains (losses)	23,611	(10,683)	(8,791)
Other income	1,142	1,375	2,185
Total revenue	4,155,573	3,934,629	3,766,065
Benefits and expenses:
Life policyholder benefits	1,558,261	1,479,272	1,374,608
Health policyholder benefits	633,778	612,725	602,610
Other policyholder benefits	35,836	36,751	38,994
Total policyholder benefits	2,227,875	2,128,748	2,016,212
Amortization of deferred acquisition costs	490,403	469,063	445,625
Commissions, premium taxes, and non-deferred acquisition expenses	264,860	249,174	237,541
Other operating expense	257,255	232,064	223,858
Interest expense	84,532	83,345	76,642
Total benefits and expenses	3,324,925	3,162,394	2,999,878
Income before income taxes	830,648	772,235	766,187
Income taxes	627,615	(232,645)	(249,894)
Income from continuing operations	1,458,263	539,590	516,293
Discontinued operations:
Income (loss) from discontinued operations, net of tax	(3,769)	10,189	10,807
Net income	$ 1,454,494	$ 549,779	$ 527,100
Basic net income per common share:
Continuing operations (in dollars per share)	$ 12.53	$ 4.50	$ 4.13
Discontinued operations (in dollars per share)	(0.03)	0.08	0.08
Total basic net income per common share (in dollars per share)	12.50	4.58	4.21
Diluted net income per common share:
Continuing operations (in dollars per share)	12.26	4.41	4.07
Discontinued operations (in dollars per share)	(0.04)	0.08	0.09
Total diluted net income per common share (in dollars per share)	$ 12.22	$ 4.49	$ 4.16

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income	$ 1,454,494	$ 549,779	$ 527,100
Unrealized investment gains (losses):
Total unrealized investment gains (losses)	921,421	553,801	(1,166,032)
Less applicable (taxes) benefits	(322,553)	(193,820)	408,092
Unrealized gains (losses) on investments, net of tax	598,868	359,981	(757,940)
Unrealized gains (losses) attributable to deferred acquisition costs	(538)	(2,412)	8,682
Less applicable (taxes) benefits	188	845	(3,039)
Unrealized gains (losses) attributable to deferred acquisition costs, net of tax	(350)	(1,567)	5,643
Foreign exchange translation adjustments, other than securities	11,389	2,178	(20,651)
Less applicable (taxes) benefits	(2,937)	(838)	6,892
Foreign exchange translation adjustments, other than securities, net of tax	8,452	1,340	(13,759)
Pension adjustments:
Amortization of pension costs	12,436	10,168	14,586
Plan amendments	0	0	(2,104)
Experience gain (loss)	(31,933)	(31,902)	(11,632)
Pension adjustments	(19,497)	(21,734)	850
Less applicable (taxes) benefits	6,827	7,607	(299)
Pension adjustments, net of tax	(12,670)	(14,127)	551
Other comprehensive income (loss)	594,300	345,627	(765,505)
Comprehensive income (loss)	2,048,794	895,406	(238,405)
Securities
Unrealized investment gains (losses):
Unrealized holding gains (losses) arising during period	950,088	544,886	(1,163,417)
Reclassification adjustment for (gains) losses on securities included in net income	(34,954)	10,645	9,478
Reclassification adjustment for amortization of (discount) premium	(47)	(4,185)	(6,346)
Foreign exchange adjustment on securities recorded at fair value	1,326	312	(3,010)
Total unrealized investment gains (losses)	916,413	551,658	(1,163,295)
Other
Unrealized investment gains (losses):
Unrealized holding gains (losses) arising during period	5,008	2,503	(1,635)
Reclassification adjustment for (gains) losses on securities included in net income	0	(360)	(1,102)
Total unrealized investment gains (losses)	$ 5,008	$ 2,143	$ (2,737)

Consolidated Statements of Shar

Consolidated Statements of Shareholder's Equity - USD ($) $ in Thousands		Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock
Beginning balance at Dec. 31, 2014		$ 4,697,466	$ 0	$ 134,218	$ 457,613	$ 997,452	$ 3,376,846	$ (268,663)
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)		(238,405)				(765,505)	527,100
Common dividends declared ($.54 in 2015, $.56 in 2016 and $.60 in 2017 a share)		(67,182)					(67,182)
Acquisition of treasury stock		(418,526)						(418,526)
Stock-based compensation		28,664			21,813		(2,132)	8,983
Exercise of stock options		53,535			17,577		(36,322)	72,280
Retirement of treasury stock		0		(4,000)	(14,719)		(183,941)	202,660
Ending balance at Dec. 31, 2015		4,055,552	0	130,218	482,284	231,947	3,614,369	(403,266)
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)		895,406				345,627	549,779
Common dividends declared ($.54 in 2015, $.56 in 2016 and $.60 in 2017 a share)		(66,968)					(66,968)
Acquisition of treasury stock		(404,784)						(404,784)
Stock-based compensation		26,326			19,659		(2,224)	8,891
Exercise of stock options		61,329					(53,845)	115,174
Retirement of treasury stock		0		(3,000)	(11,522)		(150,313)	164,835
Ending balance at Dec. 31, 2016		4,566,861	0	127,218	490,421	577,574	3,890,798	(519,150)
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)		2,048,794				594,300	1,454,494
Common dividends declared ($.54 in 2015, $.56 in 2016 and $.60 in 2017 a share)		(69,494)					(69,494)
Acquisition of treasury stock		(412,989)						(412,989)
Stock-based compensation		37,034			30,190		(606)	7,450
Exercise of stock options		61,215					(38,333)	99,548
Reclassification, Tax Reform	[1]					252,400	(252,400)
Retirement of treasury stock		0		(3,000)	(12,135)		(178,251)	193,386
Ending balance at Dec. 31, 2017		$ 6,231,421	$ 0	$ 124,218	$ 508,476	$ 1,424,274	$ 4,806,208	$ (631,755)
[1]	Income tax effects of certain items were reclassified from accumulated other comprehensive income to retained earnings to remove stranded tax effects as a result of early adoption of ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. See further discussion in Note 1—Significant Accounting Policies.

Consolidated Statements Of Sha7

Consolidated Statements Of Shareholder's Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Common dividends declared, per share (in dollars per share)	$ 0.6	$ 0.56	$ 0.54

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash provided from (used for) operating activities:
Net income	$ 1,454,494	$ 549,779	$ 527,100
Adjustments to reconcile net income from continuing operations to cash provided from continuing operations:
Loss (Income) from discontinued operations, net of income taxes	3,769	(10,189)	(10,807)
Increase (decrease) in future policy benefits	687,407	645,844	631,202
Increase (decrease) in other policy benefits	31,784	24,668	14,609
Deferral of policy acquisition costs	(660,134)	(635,318)	(612,181)
Amortization of deferred policy acquisition costs	490,403	469,063	445,625
Change in current and deferred income taxes	(700,660)	152,210	103,558
Realized (gains) losses on sale of investments and properties	(23,611)	10,683	8,791
Other, net	67,933	20,079	13,985
Net cash provided from (used for) continuing operations	1,351,385	1,226,819	1,121,882
Net cash provided from (used for) discontinued operations	77,673	171,889	(1,832)
Cash provided from (used for) operating activities	1,429,058	1,398,708	1,120,050
Cash provided from (used for) investing activities:
Fixed maturities available for sale—sold	67,246	340,434	226,792
Fixed maturities available for sale—matured, called, and repaid	488,843	236,353	376,158
Other long-term investments	3,534	1,217	3,740
Total investments sold or matured	559,623	578,004	606,690
Acquisition of investments:
Fixed maturities—available for sale	(1,314,609)	(1,530,053)	(1,070,908)
Other long-term investments	(55,096)	(20,444)	(31,707)
Total investments acquired	(1,369,705)	(1,550,497)	(1,102,615)
Net (increase) decrease in policy loans	(21,554)	(15,513)	(20,353)
Net (increase) decrease in short-term investments	(55,031)	(17,274)	(38,884)
Additions to properties	(20,285)	(25,162)	(36,957)
Sale of other assets	18	90	0
Investments in low-income housing interests	(19,890)	(32,084)	(41,231)
Cash provided from (used for) investing activities	(926,824)	(1,062,436)	(633,350)
Cash provided from (used for) financing activities:
Issuance of common stock	61,215	61,329	35,958
Cash dividends paid to shareholders	(68,831)	(66,931)	(66,899)
Repayment of debt	(126,875)	(250,000)	0
Proceeds from issuance of debt	125,000	400,000	0
Payment for debt issuance costs	(1,661)	(9,638)	0
Net borrowing (repayment) of commercial paper	61,092	22,224	1,978
Excess tax benefit from stock option exercises	0	0	17,577
Acquisition of treasury stock	(412,989)	(404,784)	(418,526)
Net receipts (payments) from deposit-type product	(90,932)	(71,991)	(95,793)
Cash provided from (used for) financing activities	(453,981)	(319,791)	(525,705)
Effect of foreign exchange rate changes on cash	(5,853)	(1,701)	34,369
Increase (decrease) in cash	42,400	14,780	(4,636)
Cash at beginning of year	76,163	61,383	66,019
Cash at end of year	$ 118,563	$ 76,163	$ 61,383

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Business : Torchmark Corporation (Torchmark or alternatively, the Company) through its wholly-owned subsidiaries provides a variety of life and supplemental health insurance products and annuities to a broad base of customers. Torchmark is organized into four reportable segments: life insurance, health insurance, annuity, and investment. Basis of Presentation : The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (GAAP), under guidance issued by the Financial Accounting Standards Board (FASB). The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Principles of Consolidation : The consolidated financial statements include the results of Torchmark and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. When Torchmark acquires a subsidiary or a block of business, the assets acquired and the liabilities assumed are measured at fair value at the acquisition date. Any excess of acquisition cost over the fair value of net assets is recorded as goodwill. Expenses incurred to effect the acquisition are charged to earnings as of the acquisition date. Upon acquisition, the accounts and results of operations are consolidated as of and subsequent to the acquisition date. Torchmark accounts for its variable interest entities (VIEs) under accounting guidance which clarifies the definition of a variable interest and the instructions for consolidating VIEs. Only primary beneficiaries are required or allowed to consolidate VIEs. Therefore, a company may have voting control of a VIE, but if it is not the primary beneficiary, it is not permitted to consolidate the VIE. As further described under the caption Low-Income Housing Tax Credit Interests below in this note, Torchmark holds passive interests in limited partnerships which provide investment returns through the provision of tax benefits (principally from the transfer of federal or state tax credits related to federal low-income housing). These interests are considered to be VIEs. They are not consolidated because the Company has no power to control the activities that most significantly affect the economic performance of these entities and therefore the Company is not the primary beneficiary of any of these interests. Torchmark’s involvement is limited to its limited partnership interest in the entities. Torchmark has not provided any other financial support to the entities beyond its commitments to fund its limited partnership interests, and there are no arrangements or agreements with any of the interests to provide other financial support. The maximum loss exposure relative to these interests is limited to their carrying value. Discontinued Operations : When a component of Torchmark’s business is sold or expected to be sold during the ensuing year, Torchmark considers whether the criteria of ASC 205-20, Discontinued Operations , have been met, which includes evaluating if the disposal of a component represents a strategic shift that has, or will have, a major effect on the Company. If the disposal meets the criteria for discontinued operations, the assets and liabilities are segregated and recorded in the Consolidated Balance Sheets as "Assets and Liabilities related to discontinued operations" for all periods presented. If the carrying amount of the business exceeds its estimated fair value, a loss is recognized. The results of operations for the discontinued component are reported in "Income from discontinued operations, net of tax" in the Consolidated Statements of Operations for current and prior periods. Discontinued operations are reported commencing in the period in which the business is either disposed of or meets the accounting criteria for discontinued operations, including any gain or loss recognized on the sale or adjustment of the carrying amount to the estimated fair value less cost to sell. As discussed in further detail in Note 6—Discontinued Operations , Torchmark sold one of its operating segments, Medicare Part D during 2016. The financial results of this business are excluded from Torchmark's continuing operations including the Notes to the Consolidated Financial Statements , other than Note 2—Statutory Accounting and Note 6—Discontinued Operations . Investments : Torchmark classifies all of its fixed maturity investments, which include bonds and redeemable preferred stocks, as available for sale. Investments classified as available for sale are carried at fair value with unrealized gains and losses, net of deferred taxes, reflected directly in accumulated other comprehensive income. Policy loans are carried at unpaid principal balances. Other long-term investments include equity securities, real estate, mortgage participations, and limited partnerships. Investments in equity securities, which include common and nonredeemable preferred stocks, are reported at fair value with unrealized gains and losses, net of deferred taxes, reflected directly in accumulated other comprehensive income. Investments in real estate are reported at cost less allowances for depreciation. Depreciation is calculated on the straight-line method. Mortgage participations, a type of investment where the mortgage loan is shared among investors, are accounted for as financing receivables. Investments in limited partnerships are primarily accounted for using the cost method of accounting as Torchmark's partnership interest is minor as Torchmark lacks the ability to exercise significant influence over the partnership's operating and financial policies. The Company considers its cost method investments for impairment when the carrying value of such investments exceeds the net asset value (“NAV”). As further discussed below in Accounting Pronouncements Not Yet Adopted , the Company will adopt ASU 2016-01 on January 1, 2018 which removes the cost method for certain investments and replaces it with fair value through net income method. Under the new guidance, limited partnerships will be reported at fair value and all fluctuations in fair value will be reported through realized gains and losses. Short-term investments include investments in interest-bearing assets with original maturities of twelve months or less. Gains and losses realized on the disposition of investments are determined on a specific identification basis. Fair Value Measurements, Investments in Securities : Torchmark measures the fair value of its fixed maturities based on a hierarchy consisting of three levels which indicate the quality of the fair value measurements as described below: • Level 1— fair values are based on quoted prices in active markets for identical assets or liabilities that the Company has the ability to access as of the measurement date. • Level 2 — fair values are based on inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability, or inputs that can otherwise be corroborated by observable market data. • Level 3— fair values are based on inputs that are considered unobservable where there is little, if any, market activity for the asset or liability as of the measurement date. In this circumstance, the Company has to rely on values derived by independent brokers or internally-developed assumptions. Unobservable inputs are developed based on the best information available to the Company which may include the Company’s own data or bid and ask prices in the dealer market. The great majority of Torchmark's fixed maturities are not actively traded and direct quotes are not generally available. Management therefore determines the fair values of these securities after consideration of data provided by third-party pricing services, independent broker/dealers, and other resources. At December 31, 2017 , Torchmark's investments in fixed maturities were primarily composed of the following significant security types: Corporate securities, state and municipal securities, redeemable preferred stocks, and U.S. government securities. The remaining security types represented less than 1% of the total in the aggregate. Over 95% of the fair value reported at December 31, 2017 was determined using data provided by third-party pricing services. Prices provided by these services are not binding offers, but are estimated exit values. Third-party pricing services use proprietary pricing models to determine security values by discounting cash flows using a market-adjusted spread to a benchmark yield. For all asset classes within Torchmark’s significant security types, third-party pricing services use a common valuation technique to model the price of the investments using observable market data. The foundation for these models consists of developing yield spreads based on multiple observable market inputs, including but not limited to: benchmark yield curves, actual trading activity, new issue yields, broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, sector-specific data, economic data, and other inputs that are corroborated in the market. Pricing vendors monitor and review their pricing data continuously with current market and economic data feeds, augmented by ongoing communication within the dealer community. Using the observable market inputs described above, spreads to an appropriate benchmark yield are further developed by the vendors for each security based on security-specific and/or sector-specific risk factors, such as a security’s terms and conditions (coupon, maturity, and call features), credit rating, sector, liquidity, collateral or other cash flow options, and other factors that could impact the risk of the security. Embedded repayment options, such as call and redemption features, are also taken into account in the pricing models. When the spread is determined, it is added to the security’s benchmark yield. The security's expected cash flows are discounted using this spread-adjusted yield, and the resulting present value of the discounted cash flows is the evaluated price. When third-party vendor prices are not available, the Company attempts to obtain valuations from other sources, including but not limited to broker/dealers, broker quotes, and prices on comparable securities. When valuations have been obtained for all securities in the portfolio, management reviews and analyzes the prices to ensure their reasonableness, taking into account available observable information. When two or more valuations are available for a security and the variance between the prices is 10% or less, the close correlation suggests similar observable inputs were used in deriving the price, and the mean of the prices is used. Securities valued in this manner are classified as Level 2. When the variance between two or more valuations for a security exceeds 10%, additional analysis is performed to determine the most appropriate value for that security, using resources such as broker quotes, prices on comparable securities, recent trades, and any other observable market data. Further review is performed on the available valuations to determine if they can be corroborated within reasonable tolerance to any other observable evidence. If one of the valuations or the mean of the available valuations for a security can be corroborated with other observable evidence, then the corroborated value is used and reported as Level 2. The Company uses information and analytical techniques deemed appropriate for determining the point within the range of reasonable fair value estimates that is most representative of fair value under current market conditions. Valuations that cannot be corroborated within a reasonable tolerance are classified as Level 3. Torchmark invests in a portfolio of private placement bonds which are not actively traded. This portfolio is managed by third parties. The portfolio managers provide valuations for the bonds based on a pricing matrix utilizing observable inputs, such as the benchmark treasury rate and published sector indices, and unobservable inputs such as an internally-developed credit rating. If they cannot be corroborated, the fair values are classified as Level 3. The fair values for each class of security and by valuation hierarchy level are indicated in Note 4—Investments under the caption Fair value measurements and Note 9—Postretirement Benefits under the caption Pension Plans . Fair Value Measurements, Other Financial Instruments : Fair values for cash, short-term investments, short-term debt, mortgage participations, receivables and payables approximate carrying value. Policy loans are an integral part of Torchmark’s subsidiaries’ life insurance policies in force and their fair values cannot be valued separately and apart from the insurance contracts. The fair values of Torchmark’s long-term debt issues are based on the same methodology as investments in fixed maturities. At December 31, 2017 , observable inputs were available for these debt securities and as such were classified as Level 2 in the valuation hierarchy. The fair value for each debt instrument as of December 31, 2017 is disclosed in Note 11—Debt . As described in Note 9—Postretirement Benefits , Torchmark maintains a nonqualified supplemental retirement plan. Therefore the assets which support the liability for this plan are considered general assets of the Company. These assets consist of the cash value of corporate-owned life insurance policies (COLI) and exchange traded funds (ETFs). The fair value of the insurance cash values approximates carrying value. Fair values for the ETFs are derived from direct quotes and are considered Level 1 in the valuation hierarchy. Impairment of Investments : Torchmark’s portfolio of fixed maturities fluctuates in value due to changes in interest rates in the financial markets as well as other factors. Fluctuations caused by market interest rate changes have little bearing on whether or not the investment will be ultimately recoverable. Therefore, Torchmark considers these declines in value resulting from changes in market interest rates to be temporary. In certain circumstances, however, Torchmark determines that the decline in the value of a security is other-than-temporary and writes the book value of the security down to its fair value, realizing an investment loss. The evaluation of Torchmark’s securities for other-than-temporary impairments is a process that is undertaken at least quarterly and is overseen by a team of investment and accounting professionals. Each security, which is impaired because the fair value is less than the cost or amortized cost, is identified and evaluated. The determination that an impairment is other-than-temporary is highly subjective and involves the careful consideration of many factors. Among the factors considered are: • The length of time and extent to which the security has been impaired • The reason(s) for the impairment • The financial condition of the issuer and the prospects for recovery in fair value of the security • The Company’s ability and intent to hold the security until anticipated recovery • Expected future cash flows The relative weight given to each of these factors can change over time as facts and circumstances change. In many cases, management believes it is appropriate to give relatively more weight to prospective factors than to retrospective factors. Prospective factors that are given more weight include prospects for recovery, the Company’s ability and intent to hold the security until anticipated recovery, and expected future cash flows. Among the facts and information considered in the process are: • Financial statements of the issuer • Changes in credit ratings of the issuer • The value of underlying collateral • News and information included in press releases issued by the issuer • News and information reported in the media concerning the issuer • News and information published by or otherwise provided by credit analysts • The nature and amount of recent and expected future sources and uses of cash • Default on a required payment • Issuer bankruptcy filings While all available information is taken into account, it is difficult to predict the ultimate recoverable amount of a distressed or impaired security. If a security is determined to be other-than-temporarily impaired, the cost basis of the security is written down to fair value and is treated as a realized loss in the period the determination is made. The written-down security will be amortized and revenue recognized in accordance with estimated future cash flows. Current accounting guidance is such that if an entity intends to sell or if it is more likely than not that it will be required to sell an impaired security prior to recovery of its cost basis, the security is to be considered other-than-temporarily impaired and the full amount of impairment must be charged to earnings. Otherwise, losses on fixed maturities which are other-than-temporarily impaired are separated into two categories, the portion of loss which is considered credit loss and the portion of loss which is due to other factors. The credit loss portion is charged to earnings while the loss due to other factors is charged to other comprehensive income. The credit loss portion of an impairment is determined as the difference between the security’s amortized cost and the present value of expected future cash flows discounted at the security’s original effective yield rate. The temporary portion is the difference between this present value of expected future cash flows and fair value (as discounted by a market yield). The expected cash flows are determined using judgment and the best information available to the Company. Inputs used to derive expected cash flows include expected default rates, current levels of subordination, and loan-to-collateral value ratios. Cash : Cash consists of balances on hand and on deposit in banks and financial institutions. Accrued investment income : Accrued investment income consists of interest income or dividends earned on the investment portfolio, but are yet to be received as of the balance sheet date. Other Receivables : Other receivables consist mostly of agent debit balances, which primarily represent commissions advanced to insurance agents. These balances are repaid to the Company over time as the premiums associated with the advanced commissions are collected by the Company and the agents' commissions on such premiums are retained. The balances were $378 million and $353 million at December 31, 2017 and 2016 , respectively. Management believes these balances are recoverable as they are less than the estimated present value of future commissions. Deferred Acquisition Costs : Certain costs of acquiring new insurance business are deferred and recorded as an asset. These costs are essential for the acquisition of new insurance business and are directly related to the successful issuance of an insurance contract including sales commissions, policy issue costs, and underwriting costs. Additionally, deferred acquisition costs (DAC) include the value of business acquired (VOBA), which are the costs of acquiring blocks of insurance from other companies or through the acquisition of other companies. These costs represent the difference between the fair value of the contractual insurance assets acquired and liabilities assumed compared against the assets and liabilities for insurance contracts that the Company issues or holds measured in accordance with GAAP. DAC and VOBA are amortized in a systematic manner which matches these costs with the associated revenues. Policies other than universal life-type policies are amortized with interest over the estimated premium-paying period of the policies in a manner which charges each year’s operations in proportion to the receipt of premium income. Universal life-type policies are amortized with interest in proportion to estimated gross profits. The assumptions used to amortize acquisition costs with regard to interest, mortality, morbidity, and persistency are consistent with those used to estimate the liability for future policy benefits. For interest-sensitive and deposit-balance type products, these assumptions are reviewed on a regular basis and are revised if actual experience differs significantly from original expectations. For all other products, amortization assumptions are generally not revised once established. DAC are subject to periodic recoverability and loss recognition testing to determine if there is a premium deficiency. These tests evaluate whether the present value of future contract-related cash flows will support the capitalized DAC asset. These cash flows consist primarily of premium income, less benefits and expenses taking inflation into account. The present value of these cash flows, less the benefit reserve, is then compared with the unamortized deferred acquisition cost balance. In the event the estimated present value of net cash flows is less, the deficiency would be recognized by a charge to earnings and either a reduction of unamortized acquisition costs or an increase in the liability for future benefits, as described under the caption Future Policy Benefits . Advertising Costs : Costs related to advertising are generally charged to expense as incurred. However, certain Globe Life Direct Response advertising costs are capitalized when there is a reliable and demonstrated relationship between total costs and future benefits that is a direct result of incurring these costs. Globe Life Direct Response advertising costs consist primarily of the production and distribution costs of direct mail advertising materials, and when capitalized are included as a component of DAC. They are amortized in the same manner as other DAC. Globe Life Direct Response advertising costs charged to earnings and included in other operating expense were $9.3 million , $9.3 million , and $9.7 million in 2017 , 2016 , and 2015 , respectively. At December 31, 2017 , unamortized capitalized advertising costs included within DAC were $1.28 billion at December 31, 2017 and $1.25 billion at December 31, 2016 . Goodwill : The excess cost of a business acquired over the fair value of net assets acquired is reported as goodwill. Goodwill is subject to impairment testing in accordance with GAAP on an annual basis, or whenever potential impairment triggers occur. The Company may perform a qualitative analysis under certain circumstances, or perform a two-step quantitative analysis. In the qualitative analysis, the Company determines if it is more likely than not that the fair value of a reporting unit is less than its carrying amount by assessing current events and circumstances. If there are factors present indicating potential impairment, the Company would proceed to the two-step quantitative analysis. In the two-step quantitative analysis, the Company utilizes two approaches, income and market, to determine the fair value of each reporting unit. In the income approach, judgment and assumptions are used in developing the projected cash flows for the reporting units, and such estimates are subject to change. The Company also exercises judgment in the determination of the discount rate as management believes this to be appropriate for the risk associated with the cash flow expectations. In the market approach, the Company utilizes the share price and a control premium based on businesses with similar assets to determine a fair value. In both cases, the fair value of each reporting unit is then measured against that reporting unit’s corresponding carrying value. In the event the fair value is less than the carrying value, further testing is required under the accounting guidance to determine the amount of impairment, if any. If there is an impairment in the goodwill of any reporting unit, it is written down and charged to earnings in the period of the test. Torchmark tested its goodwill annually as of June 30th in each of the years 2015 through 2017 . Torchmark’s goodwill was not impaired in any of those periods. Low-Income Housing Tax Credit Interests : Torchmark invests in limited partnerships that provide low-income housing tax credits and other related federal income tax benefits to Torchmark. The carrying value of Torchmark’s investment in these entities was $228 million and $280 million at December 31, 2017 and 2016 , respectively and was included in "Other assets" on the Consolidated Balance Sheets. As of December 31, 2017 , Torchmark was obligated under future commitments of $34 million , which are recorded in "Other liabilities". For guaranteed investments acquired prior to January 1, 2015, the Company utilizes the effective-yield method of amortization while the proportional method of amortization is utilized for all non-guaranteed as well as guaranteed investments acquired on or after January 1, 2015. All amortization expense is recorded in "Income tax benefit (expense)" on the Consolidated Statements of Operations . Property and Equipment : Property and equipment, included in “Other assets,” is reported at cost less allowances for depreciation. Depreciation is recorded primarily on the straight line method over the estimated useful lives of these assets which range from three to five years for equipment and ten to forty years for buildings and improvements. Ordinary maintenance and repairs are charged to income as incurred. Impairments, if any, are recorded when certain events and circumstances become evident that the fair value of the asset is less than its carrying amount. Original cost of property and equipment was $217 million at December 31, 2017 and $196 million at December 31, 2016 . Accumulated depreciation was $109 million at year end 2017 and $99 million at the end of 2016 . Depreciation expense was $10.5 million in 2017 , $9.8 million in 2016 , and $8.0 million in 2015 . Internally generated software costs are expensed as incurred in the preliminary project phase and post-implementation phase, and will be capitalized during the application development stage. Future Policy Benefits : The liability for future policy benefits for annuity and universal life-type products is represented by policy account value. The liability for future policy benefits for all other life and health products, approximately 87% of total future policy benefits, is determined on the net level premium method. This method provides for the present value of expected future benefit payments less the present value of expected future net premiums, based on estimated investment yields, mortality, morbidity, persistency and other assumptions which were considered appropriate at the time the policies were issued. For limited-payment contracts, a deferred profit liability is also recorded which causes profits to emerge over the life of the contract in proportion to policies in force. Assumptions used for traditional life and health insurance products are based primarily on Company experience. Assumptions for interest rates range from 2.5% to 7.0% for Torchmark’s insurance companies with an overall weighted average assumed rate of 5.80% . Mortality tables used for individual life insurance include various statutory tables and modifications of a variety of generally accepted actuarial tables. Morbidity assumptions for individual health are based on Company experience and industry data. Withdrawal and termination assumptions are based on Torchmark’s experience. Once established, assumptions for these products are generally not changed. An additional provision is made on most products to allow for possible adverse deviation from the assumptions. These estimates are reviewed annually and compared with actual experience. If it is determined that existing contract liabilities, together with the present value of future gross premiums, will not be sufficient to cover the present value of future benefits and to recover unamortized deferred acquisition costs, then a premium deficiency exists. Such a deficiency would be recognized immediately by a charge to earnings and either a reduction of unamortized deferred acquisition costs or an increase in the liability for future policy benefits. From that point forward, the liability for future policy benefits would be based on revised assumptions. Policy Claims and Other Benefits Payable : Torchmark establishes a liability for known policy benefits payable and an estimate of claims that have been incurred but not yet reported to the Company. Torchmark makes an estimate of unreported claims after careful evaluation of all information available to the Company. This estimate is based on prior experience and is reviewed quarterly. However, there is no certainty the stated liability for claims and other benefits, including the estimate of unsubmitted claims, will be Torchmark’s ultimate obligation. Income Taxes : Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement book values and tax bases of assets and liabilities. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. On December 22, 2017, the Tax Cuts and Jobs Act (Tax Legislation) was enacted into law which changed existing tax law, including a reduction of the corporate income tax rate from 35% to 21% effective January 1, 2018. The Company recorded $877 million of tax benefits in net income in 2017 as a result of re-measuring its deferred assets and liabilities using the lower corporate tax rate as of the date of enactment. Based on the analysis of the Tax Legislation, the Company was able to determine that this amount is a reasonable estimate of the impact of the Tax Legislation in accordance with SEC Staff Accounting Bulletin (SAB) No. 118. However, the Company will continue to analyze relevant information to complete the accounting for income taxes which may result in an adjustment to tax expense in 2018. The accounting is expected to be complete when the 2017 U.S. corporate income tax returns are filed later in 2018. More information concerning income taxes is provided in Note 8—Income Taxes . Postretirement Benefits : Torchmark accounts for its postretirement defined benefit plans by recognizing the funded status of those plans on its Consolidated Balance Sheets in accordance with accounting guidance. Periodic gains and losses attributable to changes in plan assets and liabilities that are not recognized as components of net periodic benefit costs are recognized as components of other comprehensive income, net of tax. More information concerning the accounting and disclosures for postretirement benefits is found in Note 9—Postretirement Benefits . Treasury Stock : Torchmark accounts for purchases of treasury stock on the cost method. Issuance of treasury stock is accounted for using the weighted-average cost method. More information is found in Note 12—Shareholders' Equity . Recognition of Premium Revenue and Related Expenses : Premium income for traditional long-duration life and health insurance products is recognized evenly over the contract period and when due from the policyholder. Premiums for short-duration health contracts are recognized as revenue over the contract period in proportion to the insurance protection provided. Premiums for universal life-type and annuity contracts are added to the policy account value, and revenues for such products are recognized as charges to the policy account value for mortality, administration, and surrenders (retrospective deposit method). Life premium includes policy charges of $17 million , $18 million , and $19 m

Statutory Accounting

Statutory Accounting	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Statutory Accounting	Statutory Accounting Life insurance subsidiaries of Torchmark are required to file statutory financial statements with state insurance regulatory authorities. Accounting principles used to prepare these statutory financial statements differ from GAAP. Consolidated net income and shareholders’ equity (capital and surplus) on a statutory basis for the insurance subsidiaries were as follows: Net Income Shareholders’ Equity Year Ended December 31, At December 31, 2017 2016 2015 2017 2016 Life insurance subsidiaries $ 426,285 $ 429,563 $ 393,466 $ 1,254,875 $ 1,335,070 The excess, if any, of shareholder’s equity of the insurance subsidiaries on a GAAP basis over that determined on a statutory basis is not available for distribution by the insurance subsidiaries to Torchmark without regulatory approval. Insurance subsidiaries’ statutory capital and surplus necessary to satisfy regulatory requirements in the aggregate was $458 million at December 31, 2017 . More information on the restrictions on the payment of dividends can be found in Note 12—Shareholders’ Equity . Torchmark’s statutory financial statements are presented on the basis of accounting practices prescribed by the insurance department of the state of domicile of each insurance subsidiary. While all states have adopted the National Association of Insurance Commissioners’ (NAIC) statutory accounting practices (NAIC SAP) as the basis for statutory accounting, certain states have retained prescribed practices of their respective insurance code or administrative code which can differ from NAIC SAP. For Torchmark’s life insurance companies, there are no significant differences between NAIC SAP and the accounting practices prescribed by the states of domicile.

Supplemental Information about

Supplemental Information about Changes to Accumulated Other Comprehensive Income	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Supplemental Information about Changes to Accumulated Other Comprehensive Income	Supplemental Information about Changes to Accumulated Other Comprehensive Income An analysis in the change in balance by component of Accumulated Other Comprehensive Income is as follows for each of the years 2015 through 2017 . Components of Accumulated Other Comprehensive Income For the 12 months ended December 31, 2015: Available Deferred Foreign Pension Total Balance at January 1, 2015 $ 1,090,273 $ (10,758 ) $ 17,386 $ (99,449 ) $ 997,452 Other comprehensive income (loss) before reclassifications, net of tax (759,976 ) 5,643 (13,759 ) (8,930 ) (777,022 ) Reclassifications, net of tax 2,036 — — 9,481 11,517 Other comprehensive income (loss) (757,940 ) 5,643 (13,759 ) 551 (765,505 ) Balance at December 31, 2015 332,333 (5,115 ) 3,627 (98,898 ) 231,947 For the 12 months ended December 31, 2016: Other comprehensive income (loss) before reclassifications, net of tax 356,016 (1,567 ) 1,340 (20,736 ) 335,053 Reclassifications, net of tax 3,965 — — 6,609 10,574 Other comprehensive income (loss) 359,981 (1,567 ) 1,340 (14,127 ) 345,627 Balance at December 31, 2016 692,314 (6,682 ) 4,967 (113,025 ) 577,574 For the 12 months ended December 31, 2017: Other comprehensive income (loss) before reclassifications, net of tax 621,619 (350 ) 8,452 (20,753 ) 608,968 Reclassifications, net of tax (22,751 ) — — 8,083 (14,668 ) Other comprehensive income (loss) 598,868 (350 ) 8,452 (12,670 ) 594,300 Reclassifications, Tax reform (1) 278,107 (1,515 ) 2,883 (27,075 ) 252,400 Balance at December 31, 2017 $ 1,569,289 $ (8,547 ) $ 16,302 $ (152,770 ) $ 1,424,274 (1) Income tax effects of certain items were reclassified from accumulated other comprehensive income to retained earnings to remove stranded tax effects as a result of early adoption of ASU No. 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . See further discussion in Note 1—Significant Accounting Policies . Reclassification adjustments out of Accumulated Other Comprehensive Income are presented below for each of the years 2015 through 2017 . Reclassification Adjustments Year Ended December 31, Component Line Item 2017 2016 2015 Affected line items in the Unrealized gains (losses) on available for sale assets: Realized (gains) losses $ (34,954 ) $ 10,285 $ 9,478 Realized investment gains (losses) Amortization of (discount) premium (47 ) (4,185 ) (6,346 ) Net investment income Total before tax (35,001 ) 6,100 3,132 Tax 12,250 (2,135 ) (1,096 ) Income taxes Total after tax (22,751 ) 3,965 2,036 Pension adjustments: Amortization of prior service cost 476 477 377 Other operating expenses Amortization of actuarial (gain) loss 11,960 9,691 14,209 Other operating expenses Total before tax 12,436 10,168 14,586 Tax (4,353 ) (3,559 ) (5,105 ) Income taxes Total after tax 8,083 6,609 9,481 Total reclassifications (after tax) $ (14,668 ) $ 10,574 $ 11,517

Investments

Investments	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investments	Investments Portfolio Composition : A summary of fixed maturities available for sale by cost or amortized cost and estimated fair value at December 31, 2017 and 2016 is as follows: 2017: Cost or Gross Gross Fair Value (1) % of Total (2) Fixed maturities available for sale: U.S. Government direct, guaranteed, and government-sponsored enterprises $ 390,646 $ 18,173 $ (1,373 ) $ 407,446 2 States, municipalities, and political subdivisions 1,091,960 127,890 (135 ) 1,219,715 7 Foreign governments 20,236 1,782 — 22,018 — Corporates, by sector: Financial 3,282,526 475,961 (23,392 ) 3,735,095 22 Utilities 1,955,737 369,406 (1,298 ) 2,323,845 14 Energy 1,619,349 226,140 (25,392 ) 1,820,097 11 Other corporate sectors 6,065,803 747,612 (20,616 ) 6,792,799 40 Total corporates 12,923,415 1,819,119 (70,698 ) 14,671,836 87 Collateralized debt obligations 59,150 20,084 (7,653 ) 71,581 — Other asset-backed securities 144,520 4,835 — 149,355 1 Redeemable preferred stocks, by sector: Financial 336,621 62,892 (2,727 ) 396,786 3 Utilities 28,553 2,132 (97 ) 30,588 — Total redeemable preferred stocks 365,174 65,024 (2,824 ) 427,374 3 Total fixed maturities $ 14,995,101 $ 2,056,907 $ (82,683 ) $ 16,969,325 100 (1) Amount reported in the balance sheet. (2) At fair value. 2016: Cost or Gross Gross Fair Value (1) % of Total (2) Fixed maturities available for sale: U.S. Government direct, guaranteed, and government-sponsored enterprises $ 381,054 $ 895 $ (9,151 ) $ 372,798 3 States, municipalities, and political subdivisions 1,284,605 126,850 (1,327 ) 1,410,128 9 Foreign governments 21,701 1,438 (62 ) 23,077 — Corporates, by sector: Financial 2,963,584 285,037 (45,885 ) 3,202,736 21 Utilities 1,875,946 249,701 (12,604 ) 2,113,043 14 Energy 1,542,426 127,989 (44,324 ) 1,626,091 11 Other corporate sectors 5,601,136 424,021 (84,547 ) 5,940,610 39 Total corporates 11,983,092 1,086,748 (187,360 ) 12,882,480 85 Collateralized debt obligations 60,726 13,062 (10,285 ) 63,503 — Other asset-backed securities 56,410 621 (337 ) 56,694 — Redeemable preferred stocks, by sector: Financial 371,862 43,383 (7,218 ) 408,027 3 Utilities 28,600 798 (244 ) 29,154 — Total redeemable preferred stocks 400,462 44,181 (7,462 ) 437,181 3 Total fixed maturities $ 14,188,050 $ 1,273,795 $ (215,984 ) $ 15,245,861 100 (1) Amount reported in the balance sheet. (2) At fair value. Securities, cash, and short-term investments held on deposit with various state and federal regulatory authorities had an amortized cost and fair value, respectively, of $657 million and $753 million at December 31, 2017 and $600 million and $663 million at December 31, 2016 . A schedule of fixed maturities available for sale by contractual maturity date at December 31, 2017 is shown below on an amortized cost basis and on a fair value basis. Actual maturity dates could differ from contractual maturities due to call or prepayment provisions. Amortized Fair Fixed maturities available for sale: Due in one year or less $ 147,457 $ 149,495 Due after one year through five years 682,932 720,186 Due after five years through ten years 1,397,473 1,567,972 Due after ten years through twenty years 4,701,591 5,519,917 Due after twenty years 7,861,000 8,789,769 Mortgage-backed and asset-backed securities 204,648 221,986 $ 14,995,101 $ 16,969,325 Analysis of investment operations : Year Ended December 31, 2017 2016 2015 Net investment income is summarized as follows: Fixed maturities available for sale $ 817,213 $ 778,912 $ 747,663 Policy loans 39,578 38,436 36,763 Other long-term investments 4,991 2,786 2,021 Short-term investments 948 447 95 862,730 820,581 786,542 Less investment expense (14,845 ) (13,678 ) (12,591 ) Net investment income $ 847,885 $ 806,903 $ 773,951 An analysis of realized gains (losses) from investments is as follows: Realized investment gains (losses): Fixed maturities available for sale: Sales and other $ 35,199 $ (10,645 ) $ (9,479 ) Other-than-temporary impairments (245 ) — — Other investments (7,302 ) (38 ) 688 Loss on redemption on debt (4,041 ) — — 23,611 (10,683 ) (8,791 ) Applicable tax (6,021 ) 3,739 3,077 Realized gains (losses) from investments, net of tax $ 17,590 $ (6,944 ) $ (5,714 ) An analysis of the net change in unrealized investment gains (losses) is as follows: Fixed maturities available for sale $ 916,413 $ 551,658 $ (1,163,295 ) Other investments 5,008 2,143 (2,737 ) Net change in unrealized gains (losses) $ 921,421 $ 553,801 $ (1,166,032 ) Additional information about securities sold is as follows: At December 31, 2017 2016 2015 Fixed maturities available for sale: Proceeds from sales (1) $ 67,246 $ 358,285 $ 226,792 Gross realized gains 5,079 6,133 259 Gross realized losses (1,100 ) (32,608 ) (16,894 ) (1) Includes unsettled sales of $17.9 million at December 31, 2016 . There were no unsettled sales in 2017 or 2015. Fair value measurements : The following tables represent the fair value of fixed maturities measured on a recurring basis at December 31, 2017 and 2016 : Fair Value Measurements at December 31, 2017 Using: Description Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value Fixed maturities available for sale: U.S. Government direct, guaranteed, and government-sponsored enterprises $ — $ 407,446 $ — $ 407,446 States, municipalities, and political subdivisions 44 1,219,671 — 1,219,715 Foreign governments — 22,018 — 22,018 Corporates, by sector: Financial — 3,673,089 62,006 3,735,095 Utilities — 2,168,115 155,730 2,323,845 Energy — 1,779,281 40,816 1,820,097 Other corporate sectors — 6,468,541 324,258 6,792,799 Total corporates — 14,089,026 582,810 14,671,836 Collateralized debt obligations — — 71,581 71,581 Other asset-backed securities — 135,306 14,049 149,355 Redeemable preferred stocks, by sector: Financial — 396,786 — 396,786 Utilities — 30,588 — 30,588 Total redeemable preferred stocks — 427,374 — 427,374 Total fixed maturities $ 44 $ 16,300,841 $ 668,440 $ 16,969,325 Percentage of total — % 96.1 % 3.9 % 100.0 % Fair Value Measurements at December 31, 2016 Using: Description Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value Fixed maturities available for sale: U.S. Government direct, guaranteed, and government-sponsored enterprises $ — $ 372,798 $ — $ 372,798 States, municipalities, and political subdivisions 45,302 1,364,826 — 1,410,128 Foreign governments — 23,077 — 23,077 Corporates, by sector: Financial — 3,141,611 61,125 3,202,736 Utilities — 1,959,143 153,900 2,113,043 Energy — 1,598,976 27,115 1,626,091 Other corporate sectors — 5,623,150 317,460 5,940,610 Total corporates — 12,322,880 559,600 12,882,480 Collateralized debt obligations — — 63,503 63,503 Other asset-backed securities — 56,694 — 56,694 Redeemable preferred stocks, by sector: Financial — 408,027 — 408,027 Utilities — 29,154 — 29,154 Total redeemable preferred stocks — 437,181 — 437,181 Total fixed maturities $ 45,302 $ 14,577,456 $ 623,103 $ 15,245,861 Percentage of total 0.3 % 95.6 % 4.1 % 100.0 % The following table represents changes in fixed maturities measured at fair value on a recurring basis using significant unobservable inputs (Level 3). Analysis of Changes in Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Asset- backed securities Collateralized debt Obligations Corporates Total Balance at January 1, 2015 $ — $ 63,232 $ 512,714 $ 575,946 Total gains or losses: Included in realized gains/losses — — 1,182 1,182 Included in other comprehensive income — 11,365 (11,925 ) (560 ) Acquisitions — — 38,600 38,600 Sales — — — — Amortization — 5,536 17 5,553 Other (1) — (9,751 ) (9,782 ) (19,533 ) Transfers into (out of) Level 3 (2) — — — — Balance at December 31, 2015 — 70,382 530,806 601,188 Total gains or losses: Included in realized gains/losses — — 788 788 Included in other comprehensive income — (3,943 ) 6,403 2,460 Acquisitions — — 33,662 33,662 Sales — — — — Amortization — 5,186 17 5,203 Other (1) — (8,122 ) (12,076 ) (20,198 ) Transfers into (out of) Level 3 (2) — — — — Balance at December 31, 2016 — 63,503 559,600 623,103 Total gains or losses: Included in realized gains/losses — — — — Included in other comprehensive income 410 9,654 10,900 20,964 Acquisitions 14,000 — 21,666 35,666 Sales — — — — Amortization — 4,914 17 4,931 Other (1) (361 ) (6,490 ) (9,373 ) (16,224 ) Transfers into (out of) Level 3 (2) — — — — Balance at December 31, 2017 $ 14,049 $ 71,581 $ 582,810 $ 668,440 (1) Includes foreign exchange adjustments and principal repayments. (2) There were no transfers in or out of Level 3 during the three years ended 2017 . Acquisitions of Level 3 investments in each of the years 2015 through 2017 are comprised of private-placement fixed maturities managed by an unaffiliated third-party. Quantitative Information about Level 3 Fair Value Measurements As of December 31, 2017 Fair Value Valuation Significant Unobservable Range Weighted Asset-backed securities $ 14,049 Determination of credit spread Credit BBB BBB Discounted cash flows Discount 5.35% 5.35% Collateralized debt obligations 71,581 Discounted cash flows Discount 7.0 - 8.25% 8.03% Private placement fixed maturities $ 582,810 Determination of credit spread Credit A+ to BB- BBB Discounted cash flows Discount 2.97 - 7.27% 3.93% $ 668,440 The private placement fixed maturities and asset-backed securities reported as Level 3 are managed by third party investment managers. These securities are valued based on the contractual cash flows discounted by a yield determined as a treasury benchmark adjusted for a credit spread. The credit spread is developed from observable indices for similar public fixed maturities and unobservable indices for private fixed maturities for corresponding credit ratings. However, the credit ratings for the securities are considered unobservable inputs, as they are assigned by the third party investment manager based on a quantitative and qualitative assessment of the credit underwritten. A higher (lower) credit rating would result in a higher (lower) valuation. The collateral underlying collateralized debt obligations for which fair values are reported as Level 3 consists primarily of trust preferred securities issued by banks and insurance companies. Collateralized debt obligations are valued at the present value of expected future cash flows using an unobservable discount rate. Expected cash flows are determined by scheduling the projected repayment of the collateral assuming no future defaults, deferrals, or recoveries. The discount rate is risk-adjusted to take these items into account. A significant increase (decrease) in the discount rate will produce a significant decrease (increase) in fair value. Additionally, a significant increase (decrease) in the cash flow expectations would result in a significant increase (decrease) in fair value. For more information regarding valuation procedures, please refer to Note 1—Significant Accounting Policies under the caption Fair Value Measurements, Investments in Securities . The following table presents transfers in and out of each of the valuation levels of fair values. 2017 2016 2015 In Out Net In Out Net In Out Net Level 1 $ 42,372 $ (597 ) $ 41,775 $ 45,344 $ — $ 45,344 $ 17,252 $ (49,744 ) $ (32,492 ) Level 2 597 (42,372 ) (41,775 ) — (45,344 ) (45,344 ) 49,744 (17,252 ) 32,492 Level 3 — — — — — — — — — Transfers into Level 2 from Level 3 result from the availability of observable market data when a security is valued at the end of a period. Transfers into Level 3 occur when there is a lack of observable market information. Transfers into Level 1 from Level 2 occur when direct quotes are available; transfers from Level 1 into Level 2 result when only observable market data and no direct quotes are available. Transfers between levels are recognized as of the end of the period of transfer. Other-than-temporary impairments (OTTI) : Based on the Company's evaluation of its fixed maturities available for sale in an unrealized loss position in accordance with the OTTI policy as described in Note 1—Significant Accounting Policies , the Company concluded that there was an other-than-temporary impairment of $245 thousand ( $159 thousand , net of tax) during the year ended December 31, 2017 . For the two years ended December 31, 2016, there were no other-than-temporary impairments. As of year end 2017 , previously written down securities remaining in the portfolio were carried at a fair value of $59 million , or less than 0.4% of the fair value of the fixed maturity portfolio. Torchmark is continuously monitoring the market conditions impacting its portfolio. While adverse market conditions for an extended duration could lead to some ratings downgrades in certain sectors, Torchmark has the ability and intent to hold these investments to recovery, and does not intend to sell or expect to be required to sell any of its securities in such a position. Unrealized gains/loss analysis : The following tables disclose gross unrealized investment losses by class and major sector of investments at December 31, 2017 and December 31, 2016 for the respective periods of time in a loss position. Torchmark considers these investments to be only temporarily impaired. ANALYSIS OF GROSS UNREALIZED INVESTMENT LOSSES At December 31, 2017 Less than Twelve Months Twelve Months or Longer Total Description of Securities Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Fixed maturities available for sale: Investment grade securities: U.S. Government direct, guaranteed, and government-sponsored enterprises $ 34,388 $ (422 ) $ 47,514 $ (951 ) $ 81,902 $ (1,373 ) States, municipalities and political subdivisions 4,561 (21 ) 1,771 (9 ) 6,332 (30 ) Foreign governments — — — — — — Corporates, by sector: Financial 133,080 (652 ) 35,302 (1,429 ) 168,382 (2,081 ) Utilities 48,562 (569 ) 32,345 (729 ) 80,907 (1,298 ) Energy 23,463 (81 ) 67,775 (3,682 ) 91,238 (3,763 ) Metals and mining — — — — — — Other corporate sectors 220,661 (2,312 ) 163,886 (4,257 ) 384,547 (6,569 ) Total corporates 425,766 (3,614 ) 299,308 (10,097 ) 725,074 (13,711 ) Other asset-backed securities — — — — — — Redeemable preferred stocks, by sector: Utilities — — 5,953 (97 ) 5,953 (97 ) Total redeemable preferred stocks — — 5,953 (97 ) 5,953 (97 ) Total investment grade securities 464,715 (4,057 ) 354,546 (11,154 ) 819,261 (15,211 ) Below investment grade securities: States, municipalities and political subdivisions 200 (105 ) — — 200 (105 ) Corporates, by sector: Financial — — 84,432 (21,311 ) 84,432 (21,311 ) Energy 8,114 (104 ) 75,204 (21,525 ) 83,318 (21,629 ) Metals and mining — — — — — — Other corporate sectors 25,334 (5,066 ) 54,383 (8,981 ) 79,717 (14,047 ) Total corporates 33,448 (5,170 ) 214,019 (51,817 ) 247,467 (56,987 ) Collateralized debt obligations — — 12,347 (7,653 ) 12,347 (7,653 ) Redeemable preferred stocks, by sector: Financial — — 24,376 (2,727 ) 24,376 (2,727 ) Total redeemable preferred stocks — — 24,376 (2,727 ) 24,376 (2,727 ) Total below investment grade securities 33,648 (5,275 ) 250,742 (62,197 ) 284,390 (67,472 ) Total fixed maturities $ 498,363 $ (9,332 ) $ 605,288 $ (73,351 ) $ 1,103,651 $ (82,683 ) ANALYSIS OF GROSS UNREALIZED INVESTMENT LOSSES At December 31, 2016 Less than Twelve Months Twelve Months or Longer Total Description of Securities Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Fixed maturities available for sale: Investment grade securities: U.S. Government direct, guaranteed, and government-sponsored enterprises $ 321,133 $ (8,553 ) $ 1,404 $ (598 ) $ 322,537 $ (9,151 ) States, municipalities and political subdivisions 32,178 (1,114 ) 683 (19 ) 32,861 (1,133 ) Foreign governments 4,416 (62 ) — — 4,416 (62 ) Corporates, by sector: Financial 479,669 (18,666 ) 64,335 (4,627 ) 544,004 (23,293 ) Utilities 290,732 (11,000 ) 16,977 (1,604 ) 307,709 (12,604 ) Energy 83,064 (1,076 ) 154,908 (18,127 ) 237,972 (19,203 ) Metals and mining 5,936 (231 ) 5,789 (187 ) 11,725 (418 ) Other corporate sectors 1,564,273 (65,131 ) 68,968 (6,495 ) 1,633,241 (71,626 ) Total corporates 2,423,674 (96,104 ) 310,977 (31,040 ) 2,734,651 (127,144 ) Other asset-backed securities 41,498 (337 ) — — 41,498 (337 ) Redeemable preferred stocks, by sector: Utilities 5,857 (244 ) — — 5,857 (244 ) Total redeemable preferred stocks 5,857 (244 ) — — 5,857 (244 ) Total investment grade securities 2,828,756 (106,414 ) 313,064 (31,657 ) 3,141,820 (138,071 ) Below investment grade securities: States, municipalities and political subdivisions — — 357 (194 ) 357 (194 ) Corporates, by sector: Financial — — 83,174 (22,592 ) 83,174 (22,592 ) Energy 15,567 (385 ) 91,165 (24,736 ) 106,732 (25,121 ) Metals and mining 32,478 (172 ) 34,463 (2,023 ) 66,941 (2,195 ) Other corporate sectors 51,640 (291 ) 95,679 (10,017 ) 147,319 (10,308 ) Total corporates 99,685 (848 ) 304,481 (59,368 ) 404,166 (60,216 ) Collateralized debt obligations — — 9,714 (10,285 ) 9,714 (10,285 ) Redeemable preferred stocks, by sector: Financial — — 19,912 (7,218 ) 19,912 (7,218 ) Total redeemable preferred stocks — — 19,912 (7,218 ) 19,912 (7,218 ) Total below investment grade securities 99,685 (848 ) 334,464 (77,065 ) 434,149 (77,913 ) Total fixed maturities $ 2,928,441 $ (107,262 ) $ 647,528 $ (108,722 ) $ 3,575,969 $ (215,984 ) Gross unrealized losses decreased from $216 million at year end 2016 to $83 million at year end 2017 , a decrease of $133 million . The decrease in the gross unrealized losses from prior year was primarily attributable to the improved conditions during 2017 in the energy sector and broadly across all sectors. Additional information about fixed maturities available for sale in an unrealized loss position is as follows: Less than Twelve Total Number of issues (CUSIP numbers) held: As of December 31, 2017 92 102 194 As of December 31, 2016 407 94 501 Torchmark’s entire fixed maturity portfolio consisted of 1,502 issues at December 31, 2017 and 1,565 issues at December 31, 2016 . The weighted-average quality rating of all unrealized loss positions at amortized cost was BBB- for 2017 and BBB+ for 2016 . Other investment information : Other long-term investments consist of the following: Year Ended December 31, 2017 2016 Investment in limited partnerships $ 66,522 $ 51,509 Commercial mortgage participations (1) 39,489 — Other 2,548 2,343 Total $ 108,559 $ 53,852 (1) A mortgage participation is a legal right to a prorata interest in a mortgage loan. Torchmark did not have any invested assets that were non-income producing during the twelve months ended December 31, 2017 . Concentrations of Credit Risk : Torchmark maintains a diversified investment portfolio with limited concentration in any given issuer. At December 31, 2017 , the investment portfolio, at fair value, consisted of the following: Investment grade fixed maturities: Corporate securities 82 % Securities of state and municipal governments 7 Government-sponsored enterprises 2 Other 1 Below investment grade fixed maturities: Corporate securities 3 Other 1 Policy loans, which are secured by the underlying insurance policy values 3 Other investments 1 100 % As of December 31, 2017 , securities of state and municipal governments represented 7% of invested assets at fair value. Such investments are made throughout the U.S. At yearend 2017 , the state and municipal bond portfolio at fair value was invested in securities issued within the following states: Texas ( 29% ), Ohio ( 9% ), Washington ( 8% ), Illinois ( 7% ), Michigan ( 5% ), and Georgia ( 5% ). Otherwise, there was no concentration within any given state greater than 5% . Corporate debt securities and redeemable preferred stocks represent 85% of Torchmark's investment portfolio. These investments are spread across a wide range of industries. Below are the ten largest industry concentrations held in the corporate portfolio of corporate debt securities and redeemable preferred stocks at December 31, 2017 , based on fair value: Insurance 16 % Electric utilities 12 Oil and natural gas pipelines 7 Banks 6 Transportation 4 Oil and natural gas exploration and production 4 Chemicals 4 Real estate investment trusts 4 Food 3 Metals and mining 3 At yearend 2017 , 4% of invested assets at fair value were represented by fixed maturities rated below investment grade. Par value of these investments was $790 million , amortized cost was $702 million , and fair value was $679 million . While these investments could be subject to additional credit risk, such risk should generally be reflected in their fair value.

Deferred Acquisition Costs

Deferred Acquisition Costs	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Deferred Acquisition Costs	Deferred Acquisition Costs An analysis of DAC is as follows: Year Ended December 31, 2017 2016 2015 Balance at beginning of year $ 3,783,158 $ 3,617,135 $ 3,457,397 Additions: Deferred during period: Commissions 465,920 436,252 401,166 Other expenses 194,214 199,066 211,015 Total deferred 660,134 635,318 612,181 Foreign exchange adjustment 5,712 2,180 — Adjustment attributable to unrealized investment losses (1) — — 8,682 Total additions 665,846 637,498 620,863 Deductions: Amortized during period (490,403 ) (469,063 ) (445,625 ) Foreign exchange adjustment — — (15,500 ) Adjustment attributable to unrealized investment gains (1) (538 ) (2,412 ) — Total deductions (490,941 ) (471,475 ) (461,125 ) Balance at end of year $ 3,958,063 $ 3,783,158 $ 3,617,135 (1) Represents amounts pertaining to investments relating to universal life-type products.

Discontinued Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Discontinued Operations At December 31, 2015, Torchmark met the criteria to account for its Medicare Part D Prescription Drug Plan business as a discontinued operation. Historically, the business was a reportable segment. Effective July 1, 2016, Torchmark sold its Medicare Part D Prescription Drug Plan business to an unaffiliated third party. The sale resulted in a net gain of $1.8 million ( $1.2 million net of tax) in 2016. The operating results from discontinued operations are reflected in income for the twelve months ended December 31, 2017 . The remaining assets and liabilities reflected on the Torchmark balance sheet related to discontinued operations are receivables and payables associated with the 2016 and prior plan years that are expected to be settled in the ordinary course of business during 2018. The net assets related to discontinued operations at December 31, 2017 and 2016 were as follows: At December 31, 2017 2016 Assets: Due premiums $ 3,945 $ 8,840 Other receivables (1) 64,575 118,692 Total assets related to discontinued operations 68,520 127,532 Liabilities: Risk sharing payable 8,731 8,374 Current and deferred income taxes payable 1,077 3,820 Other (2) 40,046 15,230 Total liabilities related to discontinued operations 49,854 27,424 Net assets $ 18,666 $ 100,108 (1) At December 31, 2017 , other receivables included $65 million from Centers for Medicare and Medicaid Services (CMS). At December 31, 2016 , the comparable amounts were $50 million from CMS and $69 million from drug manufacturer rebates. (2) At December 31, 2017 , the balance included $37.3 million due to CMS. At December 31, 2016 , the balance includes $3.6 million contingent sale price reserve. Income from discontinued operations for the three years ended December 31, 2017 is as follows: Year Ended December 31, 2017 2016 2015 Revenue: Health premium $ — $ 222,840 $ 260,657 Benefits and expenses: Health policyholder benefits 3,827 183,423 213,114 Amortization of deferred acquisition costs — 3,747 3,506 Commissions, premium taxes, and non-deferred acquisition expenses 763 16,396 20,909 Other operating expense 1,209 5,377 6,502 Total benefits and expenses 5,799 208,943 244,031 Income before income taxes for discontinued operations (5,799 ) 13,897 16,626 Gain from sale of discontinued operations — 1,779 — Income taxes 2,030 (5,487 ) (5,819 ) Income from discontinued operations $ (3,769 ) $ 10,189 $ 10,807 Income taxes paid related to discontinued operations for the three years ended December 31, 2017 were as follows: Year Ended December 31, 2017 2016 2015 Income taxes paid $ 714 $ 15,271 $ 3,409

Liability for Unpaid Claims

Liability for Unpaid Claims	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Liability for Unpaid Claims	Liability for Unpaid Claims Activity in the liability for unpaid health claims is summarized as follows: Year Ended December 31, 2017 2016 2015 Balance at beginning of year $ 143,128 $ 137,120 $ 128,265 Incurred related to: Current year 520,528 510,075 502,009 Prior years (8,048 ) (1,127 ) (7,845 ) Total incurred 512,480 508,948 494,164 Paid related to: Current year 394,506 386,278 379,037 Prior years 114,237 116,662 106,272 Total paid 508,743 502,940 485,309 Balance at end of year $ 146,865 $ 143,128 $ 137,120 At the end of each period, the liability for unpaid health claims includes an estimate of claims incurred but not yet reported to the Company. Such estimates are updated regularly based upon the Company’s most recent claims data with recognition of emerging experience trends. Because of the nature of the Company’s health business, the payment lags are relatively short and most claims are fully paid within a year from the time incurred. Fluctuations in claims experience can lead to either over or under estimation of the liability for any given year. The difference between the estimate made at the end of the prior period and the actual experience during the period is reflected above under the caption “Incurred related to: Prior years.” The liability for unpaid health claims is included within “Policy claims and other benefits payable” in the Consolidated Balance Sheets . Short-Duration Contracts Although Torchmark primarily sells long-duration contracts for both life and health, the Company also has a limited amount of group health products that qualify as short-duration contracts in accordance with the applicable guidance. The following table illustrates the total incurred claims for short-duration products over the last five years for the year ended December 31, 2017 . Claim frequency is determined by duration and incurred date. For the years ended December 31, 2017 As of December 31, 2017 Cumulative incurred claims (1) Total of incurred-but-not-reported liabilities plus expected development on reported claims Cumulative number of reported claims (1) (In thousands) Accident Year 2013 2014 2015 2016 2017 2013 $ 84,111 $ 82,644 $ 83,151 $ 83,119 $ 83,103 $ — 1,337 2014 101,407 99,876 99,810 99,777 — 1,600 2015 141,667 141,460 141,259 17 2,224 2016 140,944 138,899 431 2,158 2017 134,677 24,259 1,765 Total $ 597,715 $ 24,707 (1) The incurred claims and cumulative number of reported claims for all years prior to 2017 are unaudited. This table illustrates the total cumulative paid claims and allocated claims for short-duration products over the last five years for the year ended December 31, 2017 . Cumulative paid claims (1) For the years ended December 31, Accident Year 2013 2014 2015 2016 2017 2013 $ 68,159 $ 82,408 $ 83,131 $ 83,119 $ 83,103 2014 81,054 99,545 99,791 99,777 2015 115,922 140,982 141,242 2016 114,720 138,468 2017 110,418 Total 573,008 Short-duration claim liability as of December 31, 2017 24,707 Total incurred claims & IBNR $ 597,715 (1) The cumulative paid claims for all years prior to 2017 are unaudited. Below is the reconciliation of the net incurred and paid claims development tables to the liability for "Policy claims and other benefits payable" in the Consolidated Balance Sheets . December 31, 2017 December 31, 2016 Policy claims and other benefits payable: Short-duration products $ 24,707 $ 26,721 Insurance lines other than short duration—health 122,158 116,407 Total health 146,865 143,128 Insurance lines other than short duration—life 186,429 156,437 Total policy claims and other benefits payable $ 333,294 $ 299,565

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The components of income taxes were as follows: Year Ended December 31, 2017 2016 2015 Income tax expense (benefit) from continuing operations $ (627,615 ) $ 232,645 $ 249,894 Shareholders’ equity: Other comprehensive income (loss) 318,475 186,206 (411,646 ) Tax basis compensation expense (from the exercise of stock options and vesting of restricted stock awards) in excess of amounts recognized for financial reporting purposes — — (17,577 ) $ (309,140 ) $ 418,851 $ (179,329 ) Income tax (benefit) expense from continuing operations consists of: Year Ended December 31, 2017 2016 2015 Current income tax (benefit) expense $ 138,262 $ 132,806 $ 174,284 Deferred income tax (benefit) expense (765,877 ) 99,839 75,610 $ (627,615 ) $ 232,645 $ 249,894 In each of the years 2015 through 2017 , deferred income tax (benefit) expense was incurred because of certain differences between net income before income taxes as reported on the Consolidated Statements of Operations and taxable income as reported on Torchmark’s income tax returns. As explained in Note 1—Significant Accounting Policies , these differences caused the financial statement book values of some assets and liabilities to be different from their respective tax bases. As discussed in Note 1—Significant Accounting Policies , due to the passage of the Tax Legislation before December 31, 2017, the Company recorded $877 million reduction in deferred income tax expense related to a one-time adjustment to reduce its net deferred tax liability as of December 22, 2017, as required by ASC 740 Income Taxes , due to the reduction in the income tax rate. This adjustment to the Company's net deferred tax liability included $252 million related to items included in AOCI. Although many aspects of the Tax Legislation are not effective until 2018, the Company recorded a reasonable estimate for the tax reform adjustment in accordance with SAB 118. We will continue to analyze relevant information to complete our accounting for income taxes which may result in an adjustment to our estimate in 2018. The accounting is expected to be complete when the 2017 U.S. corporate income tax return is filed later in 2018. The effective income tax rate differed from the expected 35% rate as shown below: Year Ended December 31, 2017 % 2016 % 2015 % Expected income taxes $ 290,727 35.0 $ 270,282 35.0 $ 268,165 35.0 Increase (reduction) in income taxes resulting from: Tax reform adjustment (877,400 ) (105.6 ) — — — — Low income housing investments (18,515 ) (2.2 ) (18,202 ) (2.4 ) (19,031 ) (2.5 ) Share-based awards (19,549 ) (2.4 ) (18,653 ) (2.4 ) — — Other (2,878 ) (0.4 ) (782 ) (0.1 ) 760 0.1 Income tax expense (benefit) from continuing operations $ (627,615 ) (75.6 ) $ 232,645 30.1 $ 249,894 32.6 The tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and deferred tax liabilities are presented below: December 31, 2017 2016 Deferred tax assets: Fixed maturity investments $ 8,692 $ 15,004 Carryover of tax losses 4,760 3,906 Total gross deferred tax assets 13,452 18,910 Deferred tax liabilities: Unrealized gains 380,251 315,509 Employee and agent compensation 65,576 92,131 Deferred acquisition costs 618,889 975,873 Future policy benefits, unearned and advance premiums, and policy claims 248,752 391,451 Other liabilities 11,289 3,987 Total gross deferred tax liabilities 1,324,757 1,778,951 Net deferred tax liability $ 1,311,305 $ 1,760,041 Income Tax Return : Torchmark and its subsidiaries, excluding Family Heritage Life Insurance Company (Family Heritage), file a life-nonlife consolidated federal income tax return. Family Heritage files its federal income tax return on a separate company basis. The statutes of limitations for the Internal Revenue Service's examination and assessment of additional tax are closed for all tax years prior to 2014 with respect to Torchmark’s consolidated and Family Heritage’s federal income tax returns. Management believes that adequate provision has been made in the consolidated financial statements for any potential assessments that may result from current or future tax examinations and other tax-related matters for all open years. Valuations : Torchmark has net operating loss carryforwards of approximately $22.7 million at December 31, 2017 which will begin to expire in 2033 if not otherwise used to offset future taxable income. A valuation allowance is to be provided when it is more likely than not that deferred tax assets will not be realized by the Company. No valuation allowance has been recorded relating to Torchmark’s deferred tax assets as management believes Torchmark will more likely than not have sufficient taxable income in future periods to fully realize its existing deferred tax assets. Torchmark’s tax liability is adjusted to include a provision for uncertain tax positions taken or expected to be taken in a tax return. However, during the years 2015 through 2017 , Torchmark did not have any uncertain tax positions which resulted in unrecognized tax benefits. Tax penalties: Torchmark’s continuing practice is to recognize interest and penalties related to income tax matters in income tax expense. The Company recognized interest income of $5 thousand , $9 thousand , and $11 thousand , net of federal income tax expense, in its Consolidated Statements of Operations for 2017 , 2016 , and 2015 , respectively. The Company had no accrued interest or penalties at December 31, 2017 or 2016 .

Postretirement Benefits

Postretirement Benefits	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Postretirement Benefits	Postretirement Benefits Torchmark has qualified noncontributory defined benefit pension plans and contributory savings plans which cover substantially all employees. There are also two nonqualified noncontributory supplemental executive retirement plans (SERPs) which cover a limited number of employees. The total cost of these retirement plans charged to operations was as follows: Year Ended December 31, Defined (1) Defined (2) 2017 $ 4,145 $ 28,828 2016 3,614 24,202 2015 3,429 29,230 (1) 401K plans (2) Qualified pension plans and SERPs Torchmark accrues expense for the defined contribution plans based on a percentage of the employees’ contributions. The plans are funded by the employee contributions and a Torchmark contribution equal to the amount of accrued expense. Plan contributions are both mandatory and discretionary, depending on the terms of the plan. Pension Plans : Cost for the defined benefit pension plans has been calculated on the projected unit credit actuarial cost method. All plan measurements for the defined benefit plans are as of December 31st of the respective year. The defined benefit pension plans covering the majority of employees are qualified and funded. Contributions are made to funded pension plans subject to minimums required by regulation and maximums allowed for tax purposes. Defined benefit plan contributions were $21.3 million in 2017 , $15.8 million in 2016 , and $15.5 million in 2015 . Torchmark estimates as of December 31, 2017 that it will contribute an amount in the range of $30 million to $40 million to these plans in 2018 . The actual amount of contribution may be different from this estimate. Torchmark has two SERPs, one of which is active and provides to a limited number of executives an additional supplemental defined pension benefit. The supplemental benefit is based on the participant’s qualified plan benefit without consideration to the regulatory limits on compensation and benefit payments applicable to qualified plans, except that eligible compensation is capped at $1 million . This SERP is nonqualified and unfunded. However, a Rabbi Trust has been established to support the liability for this plan. This trust consists of life insurance policies on the lives of plan participants with an unaffiliated insurance carrier as well as an investment account. Since this plan is nonqualified, the investments and the policyholder value of the insurance policies in the Rabbi Trust are not included as defined benefit plan assets, but rather assets of the Company. They are included in “Other Assets” in the Consolidated Balance Sheets . The second supplemental benefit pension plan is limited to a very select group of employees and was closed as of December 31, 1994. It provides the full benefits that an employee would have otherwise received from a defined benefit plan in the absence of the limitation on benefits payable under a qualified plan. This plan is also nonqualified and unfunded. Pension cost for both supplemental defined benefit plans is determined in the same manner as for the qualified defined benefit plans. The following table includes activity for the SERPs for the three years ended December 31, 2017 . Year Ended December 31, 2017 2016 2015 Premiums paid for insurance coverage $ 2,050 $ 2,050 $ 10,068 December 31, 2017 2016 Total investments: Company owned life insurance $ 40,273 $ 37,267 Exchange traded funds 55,442 48,999 $ 95,715 $ 86,266 Liability: Active plan $ 81,457 $ 74,687 Closed plan $ 3,008 $ 3,220 Plan assets in the funded plans consist primarily of investments in marketable fixed maturities and equity securities and are valued at fair value. Torchmark measures the fair value of its financial assets, including the assets in its benefit plans, in accordance with accounting guidance which establishes a hierarchy for asset values and provides a methodology for the measurement of value. Please refer to Note 1—Significant Accounting Policies under the caption Fair Value Measurements , Investments in Securities for a complete discussion of valuation procedures. The following table presents the assets of Torchmark’s defined benefit pension plans for the years ended December 31, 2017 and 2016 . Pension Assets by Component at December 31, 2017 Fair Value Determined by: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Amount % to Total Corporate bonds: Financial $ $ 43,451 $ $ 43,451 12 Utilities 46,144 46,144 12 Energy 25,023 25,023 7 Other corporates 65,888 65,888 17 Total corporate bonds — 180,506 — 180,506 48 Exchange traded fund (1) 164,351 164,351 43 Other bonds 256 256 — Other long-term investments 2,304 2,304 1 Guaranteed annuity contract (2) 21,202 21,202 6 Short-term investments 3,984 3,984 1 Other 5,021 5,021 1 Grand Total $ 173,356 $ 204,268 $ — $ 377,624 100 (1) A fund including marketable securities that mirror the S&P 500 index. (2) Representing a guaranteed annuity contract issued by Torchmark's subsidiary, American Income Life Insurance Company, to fund the obligations of the American Income Pension Plan. Pension Assets by Component at December 31, 2016 Fair Value Determined by: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Amount % to Total Corporate bonds: Financial $ $ 41,578 $ $ 41,578 13 Utilities 43,890 43,890 13 Energy 25,427 25,427 8 Other corporates 49,141 49,141 15 Total corporate bonds — 160,036 — 160,036 49 Exchange traded fund (1) 134,771 134,771 41 Other bonds 258 258 — Guaranteed annuity contract (2) 18,997 18,997 6 Short-term investments 7,391 7,391 2 Other 7,418 7,418 2 Grand Total $ 149,580 $ 179,291 $ — $ 328,871 100 (1) A fund including marketable securities that mirror the S&P 500 index. (2) Representing a guaranteed annuity contract issued by Torchmark's subsidiary, American Income Life Insurance Company, to fund the obligations of the American Income Pension Plan. Torchmark’s investment objectives for its plan assets include preservation of capital, preservation of purchasing power, and long-term growth. Torchmark seeks to preserve capital through investments made in high quality securities with adequate diversification by issuer and industry sector to minimize risk. The portfolio is monitored continuously for changes in quality and diversification mix. The preservation of purchasing power is intended to be accomplished through asset growth, exclusive of contributions and withdrawals, in excess of the rate of inflation. Torchmark intends to maintain investments that when combined with future plan contributions will produce adequate long-term growth to provide for all plan obligations. It is also Torchmark’s objective that the portfolio’s investment return will meet or exceed the return of a balanced market index. The majority of the securities in the portfolio are highly marketable so that there will be adequate liquidity to meet projected payments. There are no specific policies calling for asset durations to match those of benefit obligations. Allowed investments are limited to equities, fixed maturities, and short-term investments (invested cash). The assets are to be invested in a mix of equity and fixed income investments that best serve the objectives of the pension plan. Factors to be considered in determining the asset mix include funded status, annual pension expense, annual pension contributions, and balance sheet liability. Equities can include common and preferred stocks, securities convertible into equities, mutual funds and exchange traded funds that invest in equities, equity interests in limited partnerships, and other equity-related investments. Primarily, equities are listed on major exchanges and adequate market liquidity is required. Fixed maturities primarily consist of marketable debt securities rated investment grade at purchase by a major rating agency. Short-term investments include fixed maturities with maturities less than one year and invested cash. Short-term investments in commercial paper must be rated at least A-2 by Standard & Poor’s with the issuer rated investment grade. Invested cash is limited to banks rated A or higher. Investments outside of the aforementioned list are not permitted, except by prior approval of the Plan’s Trustees. The investment portfolio is to be well diversified to avoid undue exposure to a single sector, industry, business, or security. The equity and fixed maturity portfolios are not permitted to invest in any single issuer that would exceed 10% of total plan assets at the time of purchase. Torchmark does not employ any other special risk management techniques, such as derivatives, in managing the pension investment portfolio. Torchmark's equity securities include an exchange traded fund that mirrors the S&P 500 index which better aligns with a passive approach rather than an actively managed portfolio. At December 31, 2017 , there were no restricted investments contained in the portfolio. Plan contributions have been invested primarily in fixed maturity and equity securities during the three years ended December 31, 2017 . The following table discloses the assumptions used to determine Torchmark’s pension liabilities and costs for the appropriate periods. The discount and compensation increase rates are used to determine current year projected benefit obligations and subsequent year pension expense. The long-term rate of return is used to determine current year expense. Differences between assumptions and actual experience are included in actuarial gain or loss. Weighted Average Pension Plan Assumptions For Benefit Obligations at December 31: 2017 2016 Discount Rate 3.75 % 4.27 % Rate of Compensation Increase 4.37 4.31 For Periodic Benefit Cost for the Year: 2017 2016 2015 Discount Rate 4.27 % 4.64 % 4.23 % Expected Long-Term Returns 6.96 7.19 6.96 Rate of Compensation Increase 4.31 4.33 4.35 The discount rate is determined based on the expected duration of plan liabilities. A yield is then derived based on the current market yield of a hypothetical portfolio of higher-quality corporate bonds which match the liability duration. The rate of compensation increase is projected based on Company experience, modified as appropriate for future expectations. The expected long-term rate of return on plan assets is management’s best estimate of the average rate of earnings expected to be received on the assets invested in the plan over the benefit period. In determining this assumption, consideration is given to the historical rate of return earned on the assets, the projected returns over future periods, and the discount rate used to compute benefit obligations. Net periodic pension cost for the defined benefit plans by expense component was as follows: Year Ended December 31, 2017 2016 2015 Service cost—benefits earned during the period $ 17,942 $ 15,502 $ 15,902 Interest cost on projected benefit obligation 22,124 21,631 19,887 Expected return on assets (23,597 ) (23,127 ) (21,204 ) Net amortization 12,281 10,135 14,465 Recognition of actuarial loss 78 61 180 Net periodic pension cost $ 28,828 $ 24,202 $ 29,230 An analysis of the impact on other comprehensive income (loss) concerning pensions and other postretirement benefits is as follows: Year Ended December 31, 2017 2016 2015 Balance at January 1 $ (173,883 ) $ (152,149 ) $ (152,999 ) Amortization of: Prior service cost 476 477 377 Net actuarial (gain) loss (1) 11,960 9,691 14,209 Total amortization 12,436 10,168 14,586 Plan amendments — — (2,104 ) Experience gain (loss) (31,933 ) (31,902 ) (11,632 ) Balance at December 31 $ (193,380 ) $ (173,883 ) $ (152,149 ) (1) Includes amortization of postretirement benefits other than pensions of $155 thousand in 2017 , $33 thousand in 2016 , and $120 thousand in 2015 . The following table presents a reconciliation from the beginning to the end of the year of the projected benefit obligation and plan assets for pensions. This table also presents the amounts previously recognized as a component of accumulated other comprehensive income. Pension Benefits Year Ended December 31, 2017 2016 Changes in benefit obligation: Obligation at beginning of year $ 527,522 $ 476,581 Service cost 17,942 15,502 Interest cost 22,124 21,631 Plan amendments — — Actuarial loss (gain) 55,369 34,667 Benefits paid (20,351 ) (20,859 ) Obligation at end of year 602,606 527,522 Changes in plan assets: Fair value at beginning of year 328,871 307,596 Return on assets 47,832 26,377 Contributions 21,272 15,757 Benefits paid (20,351 ) (20,859 ) Fair value at end of year 377,624 328,871 Funded status at year end $ (224,982 ) $ (198,651 ) Amounts recognized in accumulated other comprehensive income consist of: Net loss (gain) $ 186,563 $ 167,313 Prior service cost 4,135 4,611 Net amounts recognized at year end $ 190,698 $ 171,924 The portion of other comprehensive income that is expected to be reflected in pension expense in 2018 is as follows: Amortization of prior service cost $ 476 Amortization of net actuarial loss 14,543 Total $ 15,019 The accumulated benefit obligation (ABO) for Torchmark’s funded defined benefit pension plans was $466 million and $411 million at December 31, 2017 and 2016 , respectively. In the nonqualified plans, the ABO was $75 million at December 31, 2017 and $69 million at 2016 . Torchmark has estimated its expected pension benefits to be paid over the next ten years as of December 31, 2017 . These estimates use the same assumptions that measure the benefit obligation at December 31, 2016 , taking estimated future employee service into account. Those estimated benefits are as follows: For the year(s) 2018 $ 20,375 2019 22,143 2020 23,840 2021 25,239 2022 27,090 2023-2027 160,075 Postretirement Benefit Plans Other Than Pensions : Torchmark provides a small postretirement life insurance benefit for most retired employees, and also provides additional postretirement life insurance benefits for certain key employees. The majority of the life insurance benefits are accrued over the working lives of active employees. Otherwise, Torchmark does not provide postretirement benefits other than pensions and the life insurance benefits described above. Torchmark’s postretirement defined benefit plans other than pensions are not funded. Liabilities for these plans are measured as of December 31 for the appropriate year. The components of net periodic postretirement benefit cost for plans other than pensions are as follows: Year Ended December 31, 2017 2016 2015 Service cost $ — $ — $ — Interest cost on benefit obligation 1,132 1,139 1,075 Expected return on plan assets — — — Net amortization 155 33 120 Recognition of net actuarial (gain) loss 167 (132 ) 367 Net periodic postretirement benefit cost $ 1,454 $ 1,040 $ 1,562 The following table presents a reconciliation of the benefit obligation and plan assets from the beginning to the end of the year. As these plans are unfunded, funded status is equivalent to the accrued benefit liability. Benefits Other Than Pensions Year Ended December 31, 2017 2016 Changes in benefit obligation: Obligation at beginning of year $ 23,721 $ 22,479 Service cost — — Interest cost 1,132 1,139 Actuarial loss (gain) 1,045 412 Benefits paid (285 ) (309 ) Obligation at end of year 25,613 23,721 Changes in plan assets: Fair value at beginning of year — — Return on assets — — Contributions 285 309 Benefits paid (285 ) (309 ) Fair value at end of year — — Funded status at year end $ (25,613 ) $ (23,721 ) Amounts recognized in accumulated other comprehensive income: Net loss (1) $ 2,682 $ 1,959 Net amounts recognized at year end $ 2,682 $ 1,959 (1) The net loss for benefit plans other than pensions reduces other comprehensive income. The table below presents the assumptions used to determine the liabilities and costs of Torchmark’s postretirement benefit plans other than pensions. Weighted Average Assumptions for Postretirement Benefit Plans Other Than Pensions For Benefit Obligations at December 31: 2017 2016 Discount Rate 3.76 % 4.29 % For Periodic Benefit Cost for the Year: 2017 2016 2015 Discount Rate 4.29 % 4.66 % 4.23 % Estimated Future Payments for Post-Retirement Benefit Plans Other Than Pensions For the year(s) 2018 $ 1,228 2019 1,278 2020 1,311 2021 1,344 2022 1,386 2023-2027 7,515

Supplemental Disclosures of Cas

Supplemental Disclosures of Cash Flow Information	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Supplemental Disclosures of Cash Flow Information	Supplemental Disclosures of Cash Flow Information The following table summarizes Torchmark’s noncash transactions, which are not reflected on the Consolidated Statements of Cash Flows: Year Ended December 31, 2017 2016 2015 Stock-based compensation not involving cash $ 37,034 $ 26,326 $ 28,664 Commitments for low-income housing interests 33,846 56,818 68,949 Exchanges of fixed maturity investments 84,312 224,901 — Net unsettled security trades — 15,020 — The following table summarizes certain amounts paid during the period: Year Ended December 31, 2017 2016 2015 Interest paid $ 82,494 $ 81,338 $ 74,792 Income taxes paid 74,379 79,790 110,650

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt	Debt The following table presents information about the terms and outstanding balances of Torchmark’s debt. Selected Information about Debt Issues As of December 31, 2017 2016 Annual Interest Rate Issue Date Periodic Interest Payments Due Outstanding Principal (Par Value) Outstanding Principal (Book Value) Outstanding Principal (Fair Value) Outstanding Principal (Book Value) Long-term debt: Notes, due 5/15/23 (3,5) 7.875 % 5/93 5/15 & 11/15 $ 165,612 $ 164,284 $ 195,786 $ 164,095 Senior Notes, due 6/15/19 (3,7) 9.250 % 6/09 6/15 & 12/15 292,647 291,888 320,697 291,424 Senior Notes, due 9/15/22 (3,7) 3.800 % 9/12 3/15 & 9/15 150,000 148,477 155,000 148,189 Junior Subordinated Debentures due 12/15/52 (4,8,12) 5.875 % 9/12 quarterly — — — 120,929 Junior Subordinated Debentures due 3/15/36 (4,6,12) 4.888 % (13) (11) quarterly 20,000 20,000 20,000 20,000 Junior Subordinated Debentures due 6/15/56 (4,9) 6.125 % 4/16 quarterly 300,000 290,460 321,120 290,403 Junior Subordinated Debentures due 11/17/57 (4,10) 5.275 % 11/17 6/15 & 12/15 125,000 123,342 122,039 — Term loan due 5/17/21 (1,6) 2.600 % (14) 6/16 monthly 98,125 98,125 98,125 100,000 1,151,384 1,136,576 1,232,767 1,135,040 Less current maturity of term loan 4,375 4,375 4,375 1,875 Total long-term debt 1,147,009 1,132,201 1,228,392 1,133,165 Short-term debt: Current maturity of term loan 4,375 4,375 4,375 1,875 Commercial paper (2) 324,250 323,692 323,692 262,600 Total short-term debt 328,625 328,067 328,067 264,475 Total debt $ 1,475,634 $ 1,460,268 $ 1,556,459 $ 1,397,640 (1) The term loan has higher priority than all other debt issues. (2) Commercial paper has priority over all other debt except the term loan. (3) All securities, other than the term loan, commercial paper and Junior Subordinated Debentures have equal priority with one another. (4) All Junior Subordinated Debentures have equal priority, but are subordinate to all other issues. (5) Not callable. (6) Callable anytime. (7) Callable subject to “make-whole” premium. (8) Redeemed on December 22, 2017. (9) Callable at any time on or after June15, 2021, and prior to this date upon the occurrence of a Tax Event or Rating Agency Event. (10) Callable at any time on or after November 17, 2022, and prior to this date upon the occurrence of a Tax Event or Rating Agency Event. (11) Assumed upon November 1, 2012 acquisition of Family Heritage. (12) Quarterly payments on the 15th of March, June, September, and December. (13) Interest paid at 3 Month LIBOR plus 330 basis points, resets each quarter. (14) Interest paid at 1 Month LIBOR plus 125 basis points, resets each month. Contractual Debt Obligations : The following table presents expected scheduled principal payments under our contractual debt obligations: Year Ended December 31, 2018 2019 2020 2021 2022 Thereafter Debt obligations $ 328,625 $ 299,522 $ 9,375 $ 77,500 $ 150,000 $ 610,612 Funded debt : On November 17, 2017, Torchmark completed the issuance and sale of $125 million in aggregate principal of Torchmark’s 5.275% Junior Subordinated Debentures due 2057. The debentures were sold in a private placement pursuant to exemptions from the registration requirements of the Securities Act of 1933. The initial purchaser of the debentures was outside the United States. The net proceeds from the sale of the debentures were $123.3 million , after giving effect to the discount payable to the initial purchaser and expenses of the offering of the debentures. Torchmark used the net proceeds from the offering of the debentures to repay the $125 million outstanding principal, plus accrued interest of $143 thousand on the 5.875% Junior Subordinated Debentures on December 22, 2017. The Debentures were due December 15, 2052 and were callable beginning December 15, 2017. O n April 5, 2016, Torchmark completed the issuance and sale of $300 million in aggregate principal of Torchmark’s 6.125% Junior Subordinated Debentures due 2056. The debentures were sold pursuant to Torchmark’s shelf registration statement on Form S-3, filed September 25, 2015. The net proceeds from the sale of the debentures were $290 million , after giving effect to the underwriting discount and expenses of the offering of the debentures. Torchmark used the net proceeds from the offering of the debentures to repay the $250 million outstanding principal, plus accrued interest of $8 million , on the 6.375% Senior Notes that were due June 15, 2016. The remaining proceeds were used for general corporate purposes. Credit Facility : On May 17, 2016, Torchmark amended its credit facility to include, as a part of the facility, the issuance of a $100 million term loan and to extend the maturity date of the entire credit facility to May 2021. The facility is further designated as a back-up credit line for a commercial paper program under which the Company may either borrow from the credit line or issue commercial paper at any time, with total commercial paper outstanding not to exceed the facility maximum of $750 million , less any letters of credit issued. Interest is charged at variable rates. The term loan will be repaid on a redemption schedule which provides for quarterly installments that began June 30, 2017 that escalate each annual period with a balloon payment of $75 million due in May 2021. Interest on the term loan is computed and paid monthly at 125 basis points plus 1 Month LIBOR. In accordance with the agreement, Torchmark is subject to certain covenants regarding capitalization. As of December 31, 2017 , the Company was in full compliance with these covenants. Commercial paper outstanding and any amortization payments of the term loan due within one year are reported as short-term debt on the Consolidated Balance Sheets . A table presenting selected information concerning Torchmark’s commercial paper borrowings is presented below. Credit Facility - Commercial Paper At December 31, 2017 2016 Balance at end of period (at par value) $ 324,250 $ 262,850 Annualized interest rate 1.78 % 0.96 % Letters of credit outstanding $ 177,000 $ 177,000 Remaining amount available under credit line 248,750 310,150 Year Ended December 31, 2017 2016 2015 Average balance outstanding during period $ 323,429 $ 301,550 $ 350,851 Daily-weighted average interest rate (annualized) 1.30 % 0.83 % 0.43 % Maximum daily amount outstanding during period $ 455,912 $ 412,676 $ 458,110

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Shareholders' Equity	Shareholders’ Equity Share Data: A summary of preferred and common share activity is presented in the following chart. Preferred Stock Common Stock Issued Treasury Stock Issued Treasury Stock 2015: Balance at January 1, 2015 — — 134,218,183 (6,287,907 ) Grants of restricted stock 6,648 Forfeitures of restricted stock (13,950 ) Vesting of performance shares 211,287 Issuance of common stock due to exercise of stock options 1,576,485 Treasury stock acquired (7,340,794 ) Retirement of treasury stock (4,000,000 ) 4,000,000 Balance at December 31, 2015 — — 130,218,183 (7,848,231 ) 2016: Grants of restricted stock 12,549 Forfeitures of restricted stock — Vesting of performance shares 159,020 Issuance of common stock due to exercise of stock options 2,184,169 Treasury stock acquired (6,694,582 ) Retirement of treasury stock (3,000,000 ) 3,000,000 Balance at December 31, 2016 — — 127,218,183 (9,187,075 ) 2017: Grants of restricted stock 9,135 Vesting of performance shares 119,896 Issuance of common stock due to exercise of stock options 1,661,808 Treasury stock acquired (5,228,868 ) Retirement of treasury stock (3,000,000 ) 3,000,000 Balance at December 31, 2017 — — 124,218,183 (9,625,104 ) Acquisition of Common Shares : Torchmark shares are acquired from time to time through open market purchases under the Torchmark stock repurchase program when it is believed to be the best use of Torchmark’s excess cash flows. Share repurchases under this program were 4.1 million shares at a cost of $325 million in 2017 , 5.2 million shares at a cost of $311 million in 2016 , and 6.3 million shares at a cost of $359 million in 2015 . When stock options are exercised, proceeds from the exercises are generally used to repurchase approximately the number of shares available with those funds in order to reduce dilution. Shares repurchased for dilution purposes were 1.1 million shares at a cost of $88 million in 2017 , 1.5 million shares at a cost of $93 million in 2016 , and 1.0 million shares at a cost of $60 million in 2015 . Retirement of Treasury Stock : Torchmark retired 3.0 million shares of treasury stock in 2017 , 3.0 million in 2016 , and 4.0 million in 2015 . Restrictions : Restrictions exist on the flow of funds to Torchmark from its insurance subsidiaries. Statutory regulations require life insurance subsidiaries to maintain certain minimum amounts of capital and surplus. Dividends from insurance subsidiaries of Torchmark are restricted based on regulations by their states of domicile . Additionally, insurance company distributions are generally not permitted in excess of statutory surplus. Subsidiaries are also subject to certain minimum capital requirements. Subsidiaries of Torchmark paid cash dividends to the Parent Company in the amount of $454 million in 2017 , $438 million in 2016 , and $466 million in 2015 . As of December 31, 2017 , dividends and transfers from insurance subsidiaries to parent available to be paid in 2018 are limited to the amount of $315 million without regulatory approval, such that $940 million was considered restricted net assets of the subsidiaries. Dividends exceeding these limitations may be available during the year pending regulatory approval. While there are no legal restrictions on the payment of dividends to shareholders from Torchmark’s retained earnings, retained earnings as of December 31, 2017 were restricted by lenders’ covenants which require the Company to maintain and not distribute $3.5 billion from its total consolidated retained earnings of $4.8 billion . Earnings Per Share : A reconciliation of basic and diluted weighted-average shares outstanding used in the computation of basic and diluted earnings per share is as follows: Year Ended December 31, 2017 2016 2015 Basic weighted average shares outstanding 116,342,529 120,001,191 125,094,628 Weighted average dilutive options outstanding 2,640,965 2,366,594 1,662,607 Diluted weighted average shares outstanding 118,983,494 122,367,785 126,757,235 For the three years ended December 31, 2017 , there were no anti-dilutive shares. Income available to common shareholders for basic earnings per share is equivalent to income available to common shareholders for diluted earnings per share.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation Torchmark’s stock-based compensation consists of stock options, restricted stock, restricted stock units, and performance shares. Certain employees and directors have been granted fixed equity options to buy shares of Torchmark stock at the market value of the stock on the date of grant, under the provisions of the Torchmark stock option plans. The options are exercisable during the period commencing from the date they vest until expiring according to the terms of the grant. Options generally expire the earlier of employee termination or option contract term, which are either seven or ten year terms. Options generally vest in accordance with the following schedule: Shares vested by period Contract Period 6 Months Year 1 Year 2 Year 3 Year 4 Year 5 Directors 7 years 100% Employees 7 years —% —% 50% 50% Employees (1) 10 years —% —% 25% 25% 25% 25% (1) Grant offered through the Torchmark Corporation 2011 Incentive Plan only. All employee options vest immediately upon retirement on or after the attainment of age 65, upon death, or disability. Torchmark generally issues shares for the exercise of stock options from treasury stock. The Company generally uses the proceeds from option exercises to buy shares of Torchmark common stock in the open market to reduce the dilution from option exercises. An analysis of shares available for grant is as follows: Available for Grant 2017 2016 2015 Balance at January 1, 5,088,461 6,872,282 8,458,593 Options expired and forfeited during year (1) 26,488 8,518 90,371 Restricted stock expired and forfeited during year (2) 46,500 — 89,745 Options granted during year (1) (1,328,513 ) (1,306,306 ) (1,334,514 ) Restricted stock, restricted stock units, and performance shares granted under the Torchmark Corporation 2011 Incentive Plan (2) (868,616 ) (486,033 ) (431,913 ) Balance at December 31, 2,964,320 5,088,461 6,872,282 (1) Plan allows for grant of options such that each grant reduces shares available for grant in a range from 0.85 share to 1 share. (2) Plan allows for grant of restricted stock such that each stock grant reduces shares available for grant in a range from 3.1 shares to 3.88 shares. A summary of stock compensation activity for each of the three years ended December 31, 2017 is presented below: 2017 2016 2015 Stock-based compensation expense recognized (1) $ 37,034 $ 26,326 $ 28,664 Tax benefit recognized 32,511 27,867 10,033 (1) No stock-based compensation expense was capitalized in any period. Additional stock compensation information is as follows at December 31: 2017 2016 Unrecognized compensation (1) $ 31,309 $ 27,334 Weighted average period of expected recognition (in years) (1) 0.86 0.89 (1) Includes restricted stock and performance shares. No equity awards were cash settled during the three years ended December 31, 2017 . Options: The following table summarizes information about stock options outstanding at December 31, 2017 . Options Outstanding Options Exercisable Range of Number Outstanding Weighted- Average Remaining Contractual Life (Years) Weighted- Average Exercise Price Number Exercisable Weighted- Average Exercise Price $29.59 - $37.40 1,421,268 2.20 $ 34.54 1,366,689 $ 34.42 50.64 1,405,725 6.39 50.64 — — 50.69 - 51.62 1,090,703 3.69 50.70 958,463 50.70 53.61 - 56.32 1,384,582 4.63 53.65 594,184 53.71 73.92 - 77.26 1,451,523 7.23 77.24 9,643 73.92 $29.59 - $77.26 6,753,801 4.89 $ 53.59 2,928,979 $ 43.79 An analysis of option activity for each of the three years ended December 31, 2017 is as follows: 2017 2016 2015 Options Weighted Average Exercise Price Options Weighted Average Exercise Price Options Weighted Average Exercise Price Outstanding—beginning of year 6,973,591 $ 44.64 7,734,841 $ 38.84 7,889,321 $ 32.91 Granted: 7-year term 933,286 77.19 834,212 50.78 1,220,751 53.62 10-year term 535,220 77.26 597,225 50.64 296,875 53.61 Exercised (1,661,808 ) 36.84 (2,184,169 ) 28.08 (1,576,485 ) 22.81 Expired and forfeited (26,488 ) 57.94 (8,518 ) 39.35 (95,621 ) 48.85 Outstanding—end of year 6,753,801 $ 53.59 6,973,591 $ 44.64 7,734,841 $ 38.84 Exercisable at end of year 2,928,979 $ 43.79 3,115,847 $ 36.81 3,774,061 $ 29.37 Additional information about Torchmark’s stock option activity as of December 31, 2017 and 2016 is as follows: 2017 2016 Outstanding options: Weighted-average remaining contractual term (in years) 4.89 4.70 Aggregate intrinsic value $ 231,277 $ 87,286 Exercisable options: Weighted-average remaining contractual term (in years) 2.99 2.96 Aggregate intrinsic value $ 137,424 $ 63,395 Selected stock option activity for the three years ended December 31, 2017 is presented below: 2017 2016 2015 Weighted-average grant-date fair value of options granted $ 12.88 $ 9.04 $ 11.97 Intrinsic value of options exercised 70,948 73,995 54,854 Cash received from options exercised 61,215 61,329 35,958 Actual tax benefit received 24,832 25,898 24,470 Additional information concerning Torchmark’s unvested options is as follows at December 31: 2017 2016 Number of shares outstanding 3,824,822 3,857,744 Weighted-average exercise price (per share) $ 61.10 $ 50.97 Weighted-average remaining contractual term (in years) 6.34 6.11 Aggregate intrinsic value $ 113,246 $ 23,891 Torchmark expects that substantially all unvested options will vest. Restricted Stock: Restricted stock grants consist of time-vested grants, restricted stock units, and performance shares. Time-vested restricted stock is available to both senior executives and directors. The employee grants generally vest over five years and the director grants vest over six months. Restricted stock units are available only to directors. They vest over six months and are not converted to shares until the directors’ retirement, death, or disability. Director restricted stock and restricted stock units are generally granted on the first work day of the year. Performance shares are granted to a limited number of senior executives. Performance shares have a three year contract life and are not settled in shares until the termination of the three -year contract period. While the grant specifies a stated target number of shares, the determination of the actual settlement in shares will be based on the achievement of certain performance objectives of Torchmark over the respective three -year contract periods. Certain executive restricted stock and performance share grants contain terms related to age that could accelerate vesting. Restricted stock units outstanding at each of the year ends 2017 , 2016 , and 2015 were 120,326 , 112,591 , and 105,679 , respectively. All restricted stock units were fully vested at the end of each year of grant. Below is the final determination of the performance share grants in 2013 to 2015: Year of grants Final settlement of shares Final settlement date 2013 159,020 February 24, 2016 2014 119,896 February 21, 2017 2015 149,898 February 27, 2018 For the 2016 and 2017 performance share grants, actual shares that could be distributed range from 0 to 335 thousand for the 2016 grants and 0 to 306 thousand shares for the 2017 grants. A summary of restricted stock grants for each of the years in the three-year period ended December 31, 2017 is presented in the table below. 2017 2016 2015 Directors restricted stock: Shares 9,135 12,549 6,648 Price per share $ 73.92 $ 57.39 $ 54.16 Aggregate value $ 675 $ 720 $ 360 Percent vested as of 12/31/17 100 % 85 % 100 % Directors restricted stock units (including dividend equivalents): Shares 7,735 6,912 7,640 Price per share $ 74.45 $ 56.74 $ 54.44 Aggregate value $ 576 $ 392 $ 416 Percent vested as of 12/31/17 100 % 100 % 100 % Performance shares: Target shares 153,000 167,500 179,500 Target price per share $ 77.26 $ 50.64 $ 53.61 Assumed adjustment for performance objectives (in shares) 106,084 (35,073 ) (58,056 ) Aggregate value $ 11,821 $ 8,482 $ 9,623 Percent vested as of 12/31/17 — % — % — % Time-vested restricted stock holders, both employees and directors, are entitled to dividend payments on the unvested stock. Restricted stock unit holders are entitled to dividend equivalents. These equivalents are granted in the form of additional restricted stock units and vest immediately upon grant. Dividend equivalents are applicable only to restricted stock units. Performance shareholders are not entitled to dividend equivalents and are not entitled to dividend payments until the shares are vested and settled. An analysis of unvested restricted stock is as follows: Executive Executive Directors Directors Total 2015: Balance at January 1, 2015 263,430 556,360 — — 819,790 Grants — 179,500 6,648 7,640 193,788 Additional performance shares (1) (58,056 ) (58,056 ) Restriction lapses (61,815 ) (211,287 ) (6,648 ) (7,640 ) (287,390 ) Forfeitures (13,950 ) (7,500 ) (21,450 ) Balance at December 31, 2015 187,665 459,017 — — 646,682 2016: Grants — 167,500 12,549 6,912 186,961 Additional performance shares (1) (35,073 ) (35,073 ) Restriction lapses (130,215 ) (159,020 ) (10,655 ) (6,912 ) (306,802 ) Forfeitures — — — Balance at December 31, 2016 57,450 432,424 1,894 — 491,768 2017: Grants — 153,000 9,135 7,735 169,870 Additional performance shares (1) 106,084 106,084 Restriction lapses (14,700 ) (119,896 ) (11,029 ) (7,735 ) (153,360 ) Forfeitures (7,500 ) (7,500 ) (15,000 ) Balance at December 31, 2017 35,250 564,112 — — 599,362 (1) Estimated additional (reduced) share grants expected due to achievement of performance criteria. An analysis of the weighted-average grant-date fair values per share of unvested restricted stock is as follows for the year 2017 : Executive Restricted Stock Executive Performance Shares Directors Restricted Stock Directors Restricted Stock Units Grant-date fair value per share at January 1, 2017 $ 38.46 $ 49.79 $ 63.39 Grants — 77.26 73.92 $ 73.92 Estimated additional performance shares 71.76 Restriction lapses (30.69 ) (72.42 ) (72.11 ) (73.92 ) Forfeitures (37.40 ) (43.85 ) Grant-date fair value per share at December 31, 2017 41.93 56.64

Business Segments

Business Segments	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Business Segments	Business Segments Torchmark is organized into four segments: life insurance, supplemental health insurance, annuities, and investments. We also have other administrative expenses reported in "Corporate & Other." Torchmark’s reportable segments are based on the insurance product lines it markets and administers: life insurance, supplemental health insurance, and annuities. These major product lines are set out as reportable segments because of the common characteristics of products within these categories, comparability of margins, and the similarity in regulatory environment and management techniques. There is also an investment segment which manages the investment portfolio, debt, and cash flow for the insurance segments and the corporate function. Torchmark's chief operating decision makers evaluate the overall performance of the operations of the Company in accordance with these segments. Life insurance products include traditional and interest-sensitive whole life insurance as well as term life insurance. Health insurance products are generally guaranteed-renewable and include Medicare Supplement, critical illness, accident, and limited-benefit supplemental hospital and surgical coverages. Annuities include fixed-benefit contracts. Torchmark markets its insurance products through a number of distribution channels, each of which sells the products of one or more of Torchmark’s insurance segments. The tables below present segment premium revenue by each of Torchmark’s distribution channels. Torchmark Corporation Premium Income by Distribution Channel For the Year 2017 Life Health Annuity Total Distribution Channel Amount % of Total Amount % of Total Amount % of Total Amount % of Total United American Independent $ 12,547 1 $ 364,128 37 $ 15 100 $ 376,690 12 Liberty National Exclusive 274,635 12 196,207 20 470,842 14 American Income Exclusive 999,279 43 89,036 9 1,088,315 33 Family Heritage Exclusive 3,193 — 253,534 26 256,727 8 Direct Response 812,907 35 73,468 8 886,375 27 Other 203,986 9 203,986 6 $ 2,306,547 100 $ 976,373 100 $ 15 100 $ 3,282,935 100 For the Year 2016 Life Health Annuity Total Distribution Channel Amount % of Total Amount % of Total Amount % of Total Amount % of Total United American Independent $ 13,733 1 $ 355,015 38 $ 38 100 $ 368,786 12 Liberty National Exclusive 270,476 12 201,798 21 472,274 15 American Income Exclusive 913,355 42 84,382 9 997,737 32 Family Heritage Exclusive 2,866 — 236,075 25 238,941 8 Direct Response 782,765 36 70,393 7 853,158 27 Other 206,138 9 206,138 6 $ 2,189,333 100 $ 947,663 100 $ 38 100 $ 3,137,034 100 For the Year 2015 Life Health Annuity Total Distribution Channel Amount % of Total Amount % of Total Amount % of Total Amount % of Total United American Independent $ 15,036 1 $ 345,330 37 $ 135 100 $ 360,501 12 Liberty National Exclusive 271,113 13 209,150 23 480,263 16 American Income Exclusive 830,903 40 80,339 9 911,242 30 Family Heritage Exclusive 2,334 — 221,091 24 223,425 8 Direct Response 746,693 36 69,610 7 816,303 27 Other 206,986 10 206,986 7 $ 2,073,065 100 $ 925,520 100 $ 135 100 $ 2,998,720 100 Due to the nature of the life insurance industry, Torchmark has no individual or group which would be considered a major customer. Substantially all of Torchmark’s business is conducted in the United States. The measure of profitability established by the chief operating decision makers for insurance segments is underwriting margin before other income and administrative expenses, in accordance with the manner the segments are managed. It essentially represents gross profit margin on insurance products before insurance administrative expenses and consists of premium, less net policy obligations, acquisition expenses, and commissions. Interest credited to net policy liabilities (reserves less deferred acquisition costs) is reflected as a component of the Investment segment in order to match this cost to the investment earnings from the assets supporting the net policy liabilities. The measure of profitability for the Investment segment is excess investment income, which represents the income earned on the investment portfolio in excess of net policy requirements and financing costs associated with Torchmark’s debt. Other than the above-mentioned interest allocations and an intersegment commission, there are no other intersegment revenues or expenses. Expenses directly attributable to corporate operations are included in the “Corporate & Other” category. Stock-based compensation expense is considered a corporate expense by Torchmark management and is included in this category. All other unallocated revenues and expenses on a pretax basis, including insurance administrative expense, are also included in the “Corporate & Other” segment category. Torchmark holds a sizable investment portfolio to support its insurance liabilities, the yield from which is used to offset policy benefit, acquisition, administrative and tax expenses. This yield or investment income is taken into account when establishing premium rates and profitability expectations of its insurance products. In holding such a portfolio, investments are sold, called, or written down from time to time, resulting in a realized gain or loss. These gains or losses generally occur as a result of disposition due to issuer calls, compliance with Company investment policies, or other reasons often beyond management’s control. Unlike investment income, realized gains and losses are incidental to insurance operations, and only overall yields are considered when setting premium rates or insurance product profitability expectations. While these gains and losses are not relevant to segment profitability or core operating results, they can have a material positive or negative result on net income. For these reasons, management removes realized investment gains and losses when it views its segment operations. Management removes items that are related to prior periods when evaluating the operating results of current periods. Management also removes non-operating items unrelated to its core insurance activities when evaluating those results. Therefore, these items are excluded in its presentation of segment results, because accounting guidance requires that operating segment results be presented as management views its business. With the exception of the administrative settlements noted in the paragraphs above, all of these items are included in “Other operating expense” in the Consolidated Statements of Operations for the appropriate year. In 2017, Torchmark recorded $8.7 million in administrative settlements ( $5.6 million after tax) where claims were not properly filed or information to support the validity of the claim had not been properly submitted. These administrative settlements were included in "Policyholder benefits" in the Consolidated Statements of Operations in 2017. As further discussed in Note 15—Commitments and Contingencies , the Company received an assessment from various state guaranty fund associations for the liquidation of Penn Treaty and its affiliate. The total estimated assessment for Torchmark's subsidiaries is approximately $9.6 million of which $1.8 million is estimated to be unrecoverable. We are anticipating the remaining amount of the assessments to be recovered through premium tax credits. The assessment expenses were considered a non-operational event and therefore were excluded from the core underwriting operations of the Company. As a result of the Tax Legislation, which is discussed in Note 1—Significant Accounting Policies , we recorded a one-time increase in stock-based compensation expense of 3.4 million ( $2.2 million after tax) due to the impact the Tax Legislation had on certain performance based equity awards. In 2016, Torchmark recorded $3.8 million in administrative settlements ( $2.5 million after tax) related to benefits paid for deaths occurring in prior years where claims had not been filed. These administrative settlements were included in "Policyholder benefits" in the Consolidated Statements of Operations in 2016. In 2015, Torchmark recorded $1.4 million in administrative settlements ( $906 thousand after tax) related to a post- closing adjustment on the sale of a former subsidiary. These administrative settlements were included in "Commissions, premium taxes, and non-deferred acquisition costs" in the Consolidated Statements of Operations in 2015. The following tables set forth a reconciliation of Torchmark’s revenues and operations by segment to its major income statement line items. See Note 1—Significant Accounting Policies for additional information concerning reconciling items of segment profits to pretax income. For the year 2017 Life Health Annuity Investment Corporate & Other Adjustments Consolidated Revenue: Premium $ 2,306,547 $ 976,373 $ 15 $ 3,282,935 Net investment income $ 847,885 847,885 Other income $ 1,270 $ (128 ) (2) 1,142 Total revenue 2,306,547 976,373 15 847,885 1,270 (128 ) 4,131,962 Expenses: Policy benefits 1,549,602 628,640 35,836 13,797 (3,4) 2,227,875 Required interest on: Policy reserves (607,007 ) (77,792 ) (49,571 ) 734,370 — Deferred acquisition costs 186,236 23,454 690 (210,380 ) — Amortization of acquisition costs 396,268 96,519 2,466 (4,850 ) (4) 490,403 Commissions, premium taxes, and non-deferred acquisition costs 177,111 86,044 32 1,673 (2,5) 264,860 Insurance administrative expense (1) 210,590 210,590 Parent expense 9,631 9,631 Stock-based compensation expense 33,654 3,380 (6) 37,034 Interest expense 84,532 84,532 Total expenses 1,702,210 756,865 (10,547 ) 608,522 253,875 14,000 3,324,925 Subtotal 604,337 219,508 10,562 239,363 (252,605 ) (14,128 ) 807,037 Non-operating items 14,128 (3,4,5,6) 14,128 Measure of segment profitability (pretax) $ 604,337 $ 219,508 $ 10,562 $ 239,363 $ (252,605 ) $ — 821,165 Deduct applicable income taxes (247,484 ) Net operating income from continuing operations 573,681 Add back income taxes applicable to segment profitability 247,484 Add (deduct) realized investment gains (losses) 23,611 Deduct administrative settlements (8,659 ) Deduct non-operating expenses (288 ) Deduct guaranty fund assessments (1,801 ) Deduct increase in stock-based compensation expense due to Tax Legislation (3,380 ) Income before income taxes per Consolidated Statement of Operations $ 830,648 (1) Administrative expense is not allocated to insurance segments. (2) Elimination of intersegment commission. (3) Administrative settlements. (4) Non-operating expense. (5) Guaranty fund assessments. (6) Recognition of a one-time increase in stock-based compensation expense due to Tax Legislation. For the year 2016 Life Health Annuity Investment Corporate & Other Adjustments Consolidated Revenue: Premium $ 2,189,333 $ 947,663 $ 38 $ 3,137,034 Net investment income $ 806,903 806,903 Other income $ 1,534 $ (159 ) (2) 1,375 Total revenue 2,189,333 947,663 38 806,903 1,534 (159 ) 3,945,312 Expenses: Policy benefits 1,475,477 612,725 36,751 3,795 (3) 2,128,748 Required interest on: Policy reserves (577,827 ) (73,382 ) (51,131 ) 702,340 — Deferred acquisition costs 178,946 23,060 807 (202,813 ) — Amortization of acquisition costs 374,499 90,385 4,179 469,063 Commissions, premium taxes, and non-deferred acquisition costs 164,476 84,819 38 (159 ) (2) 249,174 Insurance administrative expense (1) 196,598 553 (4) 197,151 Parent expense 8,587 8,587 Stock-based compensation expense 26,326 26,326 Interest expense 83,345 83,345 Total expenses 1,615,571 737,607 (9,356 ) 582,872 231,511 4,189 3,162,394 Subtotal 573,762 210,056 9,394 224,031 (229,977 ) (4,348 ) 782,918 Non-operating items 4,348 (3,4) 4,348 Measure of segment profitability (pretax) $ 573,762 $ 210,056 $ 9,394 $ 224,031 $ (229,977 ) $ — 787,266 Deduct applicable income taxes (237,906 ) Net operating income from continuing operations 549,360 Add back income taxes applicable to segment profitability 237,906 Add (deduct) realized investment gains (losses) (10,683 ) Deduct administrative settlements (3,795 ) Deduct non-operating fees (553 ) Income before income taxes per Consolidated Statement of Operations $ 772,235 (1) Administrative expense is not allocated to insurance segments. (2) Elimination of intersegment commission. (3) Administrative settlements. (4) Non-operating fees. For the Year 2015 Life Health Annuity Investment Corporate & Other Adjustments Consolidated Revenue: Premium $ 2,073,065 $ 925,520 $ 135 $ 2,998,720 Net investment income $ 773,951 773,951 Other income $ 2,379 $ (194 ) (2) 2,185 Total revenue 2,073,065 925,520 135 773,951 2,379 (194 ) 3,774,856 Expenses: Policy benefits 1,374,608 602,610 38,994 2,016,212 Required interest on: Policy reserves (552,298 ) (69,057 ) (53,295 ) 674,650 — Deferred acquisition costs 172,947 22,760 1,138 (196,845 ) — Amortization of acquisition costs 353,595 83,341 8,689 445,625 Commissions, premium taxes, and non-deferred acquisition costs 154,811 81,489 41 1,200 (2,3) 237,541 Insurance administrative expense (1) 186,191 186,191 Parent expense 9,003 9,003 Stock-based compensation expense 28,664 28,664 Interest expense 76,642 76,642 Total expenses 1,503,663 721,143 (4,433 ) 554,447 223,858 1,200 2,999,878 Subtotal 569,402 204,377 4,568 219,504 (221,479 ) (1,394 ) 774,978 Non-operating items 1,394 (3) 1,394 Measure of segment profitability (pretax) $ 569,402 $ 204,377 $ 4,568 $ 219,504 $ (221,479 ) $ — 776,372 Deduct applicable income taxes (253,459 ) Net operating income from continuing operations 522,913 Add back income taxes applicable to segment profitability 253,459 Add (deduct) realized investment gains (losses) (8,791 ) Deduct administrative settlements (1,394 ) Income before income taxes per Consolidated Statement of Operations $ 766,187 (1) Administrative expense is not allocated to insurance segments. (2) Elimination of intersegment commission. (3) Administrative settlements. Assets for each segment are reported based on a specific identification basis. The insurance segments’ assets contain DAC. The investment segment includes the investment portfolio, cash, and accrued investment income. Goodwill is assigned to the insurance segments at the time of purchase. All other assets are included in the Other category. The table below reconciles segment assets to total assets as reported in the consolidated financial statements. Assets by Segment At December 31, 2017 Life Health Annuity Investment Other Consolidated Cash and invested assets $ 17,853,047 $ 17,853,047 Accrued investment income 233,453 233,453 Deferred acquisition costs $ 3,423,296 $ 529,068 $ 5,699 3,958,063 Goodwill 309,609 131,982 441,591 Other assets $ 988,831 988,831 Total assets $ 3,732,905 $ 661,050 $ 5,699 $ 18,086,500 $ 988,831 $ 23,474,985 At December 31, 2016 Life Health Annuity Investment Other Consolidated Cash and invested assets $ 15,955,891 $ 15,955,891 Accrued investment income 223,148 223,148 Deferred acquisition costs $ 3,261,220 $ 512,701 $ 9,237 3,783,158 Goodwill 309,609 131,982 441,591 Other assets $ 1,032,299 1,032,299 Total assets $ 3,570,829 $ 644,683 $ 9,237 $ 16,179,039 $ 1,032,299 $ 21,436,087 Liabilities for each segment are reported also on a specific identification basis similar to the assets. The insurance segments' liabilities contain future policy benefits, unearned and advance premiums, and policy claims and other benefits payable. Other policyholders' funds are included in Other as well as current and deferred income taxes payable. Debt represents both short and long-term. Liabilities by Segment At December 31, 2017 Life Health Annuity Investment Other Consolidated Future policy benefits $ 10,353,286 $ 1,831,338 $ 1,254,848 $ 13,439,472 Unearned and advance premiums 16,927 44,503 61,430 Policy claims and other benefits payable 186,429 146,865 333,294 Debt $ 1,460,268 1,460,268 Other $ 1,949,100 1,949,100 Total liabilities $ 10,556,642 $ 2,022,706 $ 1,254,848 $ 1,460,268 $ 1,949,100 $ 17,243,564 At December 31, 2016 Life Health Annuity Investment Other Consolidated Future policy benefits $ 9,825,776 $ 1,706,870 $ 1,293,191 $ 12,825,837 Unearned and advance premiums 16,828 47,189 64,017 Policy claims and other benefits payable 156,437 143,128 299,565 Debt $ 1,397,640 1,397,640 Other $ 2,282,167 2,282,167 Total liabilities $ 9,999,041 $ 1,897,187 $ 1,293,191 $ 1,397,640 $ 2,282,167 $ 16,869,226

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Reinsurance : Insurance affiliates of Torchmark reinsure that portion of insurance risk which is in excess of their retention limits. Retention limits for ordinary life insurance range up to $2 million per life. Life insurance ceded represented 0.4% of total life insurance in force at December 31, 2017 . Insurance ceded on life and accident and health products represented 0.2% of premium income for 2017 . Torchmark would be liable for the reinsured risks ceded to other companies to the extent that such reinsuring companies are unable to meet their obligations. Insurance affiliates also assume insurance risks of other external companies. Life reinsurance assumed represented 1.8% of life insurance in force at December 31, 2017 and reinsurance assumed on life and accident and health products represented 0.7% of premium income for 2017 . Leases : Torchmark leases office space, office equipment, and aviation equipment under a variety of operating lease arrangements. The Company does not have any capital leases. Rental expense for operating leases for each of the three years ended December 31, 2017 is as follows: Year Ended December 31, 2017 2016 2015 Rental expense $ 6,446 $ 6,520 $ 6,722 Future minimum rental commitments required under operating leases having remaining noncancelable lease terms in excess of one year at December 31, 2017 were as follows: Year Ended December 31, 2018 2019 2020 2021 2022 Thereafter Operating lease commitments $ 3,483 $ 3,298 $ 3,124 $ 2,886 $ 1,943 $ 1,830 Purchase Commitments : Torchmark has various long-term noncancelable purchase commitments as well as commitments to provide capital for low-income housing tax credit interests. See further discussion related to tax credits in Note 1—Significant Accounting Policies . Year Ended December 31, 2018 2019 2020 2021 2022 Thereafter Purchase commitments $ 27,326 $ 9,198 $ 3,257 $ 2,213 $ 2,169 $ 246,836 Investments : As of December 31, 2017 , Torchmark is committed to purchase $210 million of commercial mortgage loan participations from a third party. Guarantees : At December 31, 2017 , Torchmark had in place four guarantee agreements, of which were either Parent Company guarantees of subsidiary obligations to a third party, or Parent Company guarantees of obligations between wholly-owned subsidiaries. As of December 31, 2017 , Torchmark had no liability with respect to these guarantees. Letters of Credit : Torchmark has guaranteed letters of credit in connection with its credit facility with a group of banks as disclosed in Note 11—Debt . The letters of credit were issued by TMK Re, Ltd., a wholly-owned subsidiary, to secure TMK Re, Ltd.’s obligation for claims on certain policies reinsured by TMK Re, Ltd. that were sold by other Torchmark insurance companies. These letters of credit facilitate TMK Re, Ltd.’s ability to reinsure the business of Torchmark’s insurance carriers. The agreement expires in 2021. The maximum amount of letters of credit available is $250 million . The Torchmark Parent Company would be liable to the extent that TMK Re, Ltd. does not pay the reinsured party. Letters of credit outstanding were $177 million at December 31, 2017 and 2016 . Equipment leases : Torchmark has guaranteed performance of certain subsidiaries as lessees under three leasing arrangements which include two for aviation equipment and one for computer software, furniture, and equipment. One aviation lease expires in August 2022 and the second expires in September 2024. The office equipment lease expired in December 2017. At December 31, 2017 , total remaining undiscounted payments under the leases were approximately $10 million . The Torchmark Parent Company would be responsible for any subsidiary obligation in the event the subsidiary did not make payments or otherwise perform under the terms of the lease. Unclaimed Property Audits : Torchmark subsidiaries are currently the subject of audits regarding the identification, reporting and escheatment of unclaimed property arising from life insurance policies and a limited number of annuity contracts. These audits are being conducted by private entities that have contracted with forty-seven states through their respective Departments of Revenue, and have not resulted in any financial assessment from any state nor indicated any liability. The audits are wide-ranging and seek large amounts of data regarding claims handling, procedures, and payments of contract benefits arising from unreported death claims. No estimate of range can be made at this time for loss contingencies related to possible administrative penalties or amounts that could be payable to the states for the escheatment of abandoned property. Litigation : Torchmark and its subsidiaries, in common with the insurance industry in general, are subject to litigation, including claims involving tax matters, alleged breaches of contract, torts, including bad faith and fraud claims based on alleged wrongful or fraudulent acts of agents of Torchmark’s subsidiaries, employment discrimination, and miscellaneous other causes of action. Based upon information presently available, and in light of legal and other factual defenses available to Torchmark and its subsidiaries, management does not believe that such litigation will have a material adverse effect on Torchmark’s financial condition, future operating results or liquidity; however, assessing the eventual outcome of litigation necessarily involves forward-looking speculation as to judgments to be made by judges, juries and appellate courts in the future. This bespeaks caution, particularly in states with reputations for high punitive damage verdicts. Torchmark’s management recognizes that large punitive damage awards bearing little or no relation to actual damages continue to be awarded by juries in jurisdictions in which Torchmark and its subsidiaries have substantial business, creating the potential for unpredictable material adverse judgments in any given punitive damage suit. On February 1, 2018, a putative class action litigation was filed against American Income Life Insurance Company in U.S. District Court for the Northern District of Texas, Dallas Division ( Bruce v. American Income Life Insurance Company, et al. , Case No. 3:18-cv-00258-G). The plaintiff, a former insurance sales agent of American Income who is suing on behalf of all current and former American Income sales agents contracted through State General Agent Stephen Jubrey’s agency office at any time since January 31, 2015 through the final disposition of this matter, asserts that such agents are employees rather than independent contractors as they are classified by American Income. He alleges failure to pay minimum wages, overtime wages and other applicable monies in accordance with the Fair Labor Standards Act. The plaintiff seeks, in a jury trial, actual and punitive damages, pre- and post-judgment interest, attorney fees, costs and other relief, including injunctive relief. With respect to its current litigation, at this time management believes that the possibility of a material judgment adverse to Torchmark is remote, and no estimate of range can be made for loss contingencies that are at least reasonably possible but not accrued. Guaranty Fund Assessment : In 2017, the Commonwealth Court of Pennsylvania issued orders placing Penn Treaty Network America Insurance Company (Penn Treaty) and affiliate American Network Insurance Company (ANIC) in liquidation due to financial difficulties. In such instances, the various state guaranty fund associations employ funding mechanisms, through assessments to their member companies, to cover the obligations of the insolvent entities. Consequently, the Company continues to receive guaranty fund assessments from the state associations related to these companies. The Company has projected its share of the ultimate assessments from these insolvencies based on assumptions about future events and its market share of premiums by state. The total estimated assessment for Torchmark's subsidiaries is approximately $9.6 million of which $7.8 million is estimated to be recoverable through state premium tax credit offsets. We anticipate the remaining $1.8 million will be unrecoverable.

Selected Quarterly Data (Unaudi

Selected Quarterly Data (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Data (Unaudited)	Selected Quarterly Data (Unaudited) The following is an unaudited summary of quarterly results for the two years ended December 31, 2017 . The information includes all adjustments (consisting of normal accruals) which management considers necessary for a fair presentation of the results of operations for these periods. Three Months Ended March 31, June 30, September 30, December 31, 2017: Premium income $ 820,631 $ 816,614 $ 819,217 $ 826,473 Net investment income 208,282 212,776 213,872 212,955 Realized investment gains (losses) (5,748 ) (705 ) 12,595 17,469 Total revenue 1,023,581 1,029,078 1,046,015 1,056,899 Policyholder benefits 557,776 556,415 551,219 562,465 Amortization of deferred acquisition costs 125,908 122,121 122,334 120,040 Pretax income from continuing operations 191,741 201,926 220,610 216,371 Income from continuing operations 137,178 140,363 153,346 1,027,376 Income from discontinued operations (3,637 ) (90 ) (12 ) (30 ) Net income 133,541 140,273 153,334 1,027,346 Basic net income per common share: Continuing operations 1.16 1.20 1.32 8.93 Discontinued operations (0.03 ) — — — Total basic net income per common share 1.13 1.20 1.32 8.93 Diluted net income per common share: Continuing operations 1.14 1.18 1.29 8.71 Discontinued operations (0.03 ) — — — Total diluted net income per common share 1.11 1.18 1.29 8.71 Three Months Ended March 31, June 30, September 30, December 31, 2016: Premium income $ 779,860 $ 785,855 $ 783,411 $ 787,908 Net investment income 197,053 201,642 202,720 205,488 Realized investment gains (losses) 293 4,005 3,482 (18,463 ) Total revenue 977,627 991,884 989,773 975,345 Policyholder benefits 524,973 531,485 532,152 540,138 Amortization of deferred acquisition costs 118,806 117,245 116,821 116,191 Pretax income from continuing operations 195,448 199,344 201,461 175,982 Income from continuing operations 133,574 139,294 141,910 124,812 Income from discontinued operations (9,541 ) (865 ) 9,959 10,636 Net income 124,033 138,429 151,869 135,448 Basic net income per common share: Continuing operations 1.10 1.16 1.19 1.05 Discontinued operations (0.08 ) (0.01 ) 0.08 0.09 Total basic net income per common share 1.02 1.15 1.27 1.14 Diluted net income per common share: Continuing operations 1.08 1.13 1.16 1.03 Discontinued operations (0.07 ) — 0.09 0.09 Total diluted net income per common share 1.01 1.13 1.25 1.12

Schedule II. Condensed Financia

Schedule II. Condensed Financial Information of Registrant	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule II. Condensed Financial Information of Registrant	TORCHMARK CORPORATION (PARENT COMPANY) SCHEDULE II. CONDENSED FINANCIAL INFORMATION OF REGISTRANT CONDENSED BALANCE SHEETS (Dollar amounts in thousands) December 31, 2017 2016 Assets: Investments: Long-term investments $ 35,562 $ 33,586 Short-term investments 5,624 — Total investments 41,186 33,586 Cash 1,008 — Investment in affiliates 7,763,704 6,004,429 Due from affiliates 95,920 96,005 Taxes receivable from affiliates 63,099 88,406 Other assets 135,616 119,801 Total assets $ 8,100,533 $ 6,342,227 Liabilities and shareholders’ equity: Liabilities: Short-term debt $ 328,067 $ 264,475 Long-term debt 1,281,971 1,282,891 Due to affiliates 8,002 — Other liabilities 251,072 228,000 Total liabilities 1,869,112 1,775,366 Shareholders’ equity: Preferred stock 351 351 Common stock 124,218 127,218 Additional paid-in capital 858,987 840,932 Accumulated other comprehensive income 1,424,274 577,574 Retained earnings 4,806,208 3,890,798 Treasury stock (982,617 ) (870,012 ) Total shareholders’ equity 6,231,421 4,566,861 Total liabilities and shareholders’ equity $ 8,100,533 $ 6,342,227 See Notes to Condensed Financial Statements and accompanying Report of Independent Registered Public Accounting Firm. TORCHMARK CORPORATION (PARENT COMPANY) SCHEDULE II. CONDENSED FINANCIAL INFORMATION OF REGISTRANT (continued) CONDENSED STATEMENTS OF OPERATIONS (Dollar amounts in thousands) Year Ended December 31, 2017 2016 2015 Net investment income $ 26,130 $ 25,352 $ 23,715 Realized investment gains (losses) (2,791 ) — 8 Total revenue 23,339 25,352 23,723 General operating expenses 61,447 52,613 54,100 Reimbursements from affiliates (52,776 ) (54,288 ) (53,436 ) Interest expense 88,474 86,853 79,677 Total expenses 97,145 85,178 80,341 Operating income (loss) before income taxes and equity in earnings of affiliates (73,806 ) (59,826 ) (56,618 ) Income taxes (9,874 ) 23,479 15,542 Net operating loss before equity in earnings of affiliates (83,680 ) (36,347 ) (41,076 ) Equity in earnings of affiliates 1,538,174 586,126 568,176 Net income 1,454,494 549,779 527,100 Other comprehensive income (loss): Attributable to Parent Company (8,409 ) (11,314 ) (3,539 ) Attributable to affiliates 602,709 356,941 (761,966 ) Comprehensive income (loss) $ 2,048,794 $ 895,406 $ (238,405 ) See Notes to Condensed Financial Statements and accompanying Report of Independent Registered Public Accounting Firm. TORCHMARK CORPORATION (PARENT COMPANY) SCHEDULE II. CONDENSED FINANCIAL INFORMATION OF REGISTRANT—(continued) CONDENSED STATEMENTS OF CASH FLOWS (Dollar amounts in thousands) Year Ended December 31, 2017 2016 2015 Net income $ 1,454,494 $ 549,779 $ 527,100 Equity in earnings of affiliates (1,538,174 ) (586,126 ) (568,176 ) Cash dividends from subsidiaries 453,904 437,566 466,416 Other, net 52,957 (6,718 ) 20,371 Cash provided from operations 423,181 394,501 445,711 Cash provided from (used for) investing activities: Net decrease (increase) in short-term investments (5,624 ) (3,466 ) 17,338 Investment in subsidiaries (31,000 ) (35,000 ) (2 ) Additions to properties (7,230 ) (21,965 ) (468 ) Loaned money to affiliates (180,000 ) (363,056 ) (282,508 ) Repayments from affiliates 180,000 318,056 282,508 Cash provided from (used for) investing activities (43,854 ) (105,431 ) 16,868 Cash provided from (used for) financing activities: Repayment of debt (126,875 ) (250,000 ) — Proceeds from issuance of debt 125,000 400,000 — Payment for debt issuance costs (1,661 ) (9,638 ) — Net issuance (repayment) of commercial paper 61,092 22,224 1,978 Issuance of stock 61,215 61,329 35,958 Acquisitions of treasury stock (412,989 ) (404,784 ) (418,526 ) Borrowed money from affiliate 278,500 60,000 15,000 Repayments to affiliates (270,500 ) (78,000 ) (15,000 ) Excess tax benefit on stock option exercises — — 8,180 Payment of dividends (92,101 ) (90,201 ) (90,169 ) Cash provided from (used for) financing activities (378,319 ) (289,070 ) (462,579 ) Net increase (decrease) in cash 1,008 — — Cash balance at beginning of period — — — Cash balance at end of period $ 1,008 $ — $ — See Notes to Condensed Financial Statements and accompanying Report of Independent Registered Public Accounting Firm. TORCHMARK CORPORATION (PARENT COMPANY) SCHEDULE II. CONDENSED FINANCIAL INFORMATION OF REGISTRANT (continued) NOTES TO CONDENSED FINANCIAL STATEMENTS (Dollar amounts in thousands) Note A—Dividends from Subsidiaries Cash dividends paid to Torchmark from the subsidiaries were as follows: Year Ended December 31, 2017 2016 2015 Dividends from subsidiaries $ 453,904 $ 437,566 $ 466,416 Note B—Supplemental Disclosures of Cash Flow Information The following table summarizes noncash transactions, which are not reflected on the Condensed Statements of Cash Flows : Year Ended December 31, 2017 2016 2015 Stock-based compensation not involving cash $ 37,034 $ 26,326 $ 28,664 Borrowed money from affiliate — — 56,503 Investment in subsidiaries 317,027 — 39,206 Purchase of agent debit balances — — 17,297 The following table summarizes certain amounts paid (received) during the period: Year Ended December 31, 2017 2016 2015 Interest paid $ 86,606 $ 84,952 $ 77,920 Income taxes paid (received) (19,961 ) (20,838 ) (22,009 ) Note C—Preferred Stock As of December 31, 2017 , Torchmark had 351 thousand shares of Cumulative Preferred Stock, Series A, issued and outstanding, of which 280 thousand shares were 6.50% Cumulative Preferred Stock, Series A, and 71 thousand shares were 7.15% Cumulative Preferred Stock, Series A (collectively, the “Series A Preferred Stock”). All issued and outstanding shares of Series A Preferred Stock were held by wholly-owned insurance subsidiaries. In the event of liquidation, the holders of the Series A Preferred Stock at the time outstanding would be entitled to receive a liquidating distribution out of the assets legally available to stockholders in the amount of $1 thousand per share or $351 million in the aggregate, plus any accrued and unpaid dividends, before any distribution is made to holders of Torchmark common stock. Holders of Series A Preferred Stock do not have any voting rights nor have rights to convert such shares into shares of any other class of Torchmark capital stock. See accompanying Report of Independent Registered Public Accounting Firm.

Schedule IV. Reinsurance

Schedule IV. Reinsurance	12 Months Ended
	Dec. 31, 2017
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Schedule IV. Reinsurance	TORCHMARK CORPORATION SCHEDULE IV. REINSURANCE (CONSOLIDATED) (Dollar Amounts in thousands) Gross Ceded (1) Assumed Net Percentage For the Year Ended December 31, 2017 Life insurance in force $ 179,902,605 $ 705,152 $ 3,211,423 $ 182,408,876 1.8 Premiums: (2) Life insurance $ 2,272,038 $ 4,437 $ 21,912 $ 2,289,513 1.0 Health insurance 980,082 3,709 — 976,373 — Total premium $ 3,252,120 $ 8,146 $ 21,912 $ 3,265,886 0.7 For the Year Ended December 31, 2016 Life insurance in force $ 174,314,897 $ 725,867 $ 3,352,113 $ 176,941,143 1.9 Premiums: (2) Life insurance $ 2,152,698 $ 4,507 $ 22,915 $ 2,171,106 1.1 Health insurance 951,137 3,474 — 947,663 — Total premium $ 3,103,835 $ 7,981 $ 22,915 $ 3,118,769 0.7 For the Year Ended December 31, 2015 Life insurance in force $ 167,677,206 $ 729,739 $ 3,498,826 $ 170,446,293 2.1 Premiums: (2) Life insurance $ 2,034,373 $ 4,484 $ 24,007 $ 2,053,896 1.2 Health insurance 928,659 3,139 — 925,520 — Total premium $ 2,963,032 $ 7,623 $ 24,007 $ 2,979,416 0.8 (1) No amounts have been netted against ceded premium. (2) Excludes policy charges of $17.0 million , $18.3 million , and $19.3 million in each of the years 2017 , 2016 , and 2015 , respectively. See accompanying Report of Independent Registered Public Accounting Firm.

Significant Accounting Polici27

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Significant Accounting Policies [Line Items]
Basis of Presentation	Basis of Presentation : The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (GAAP), under guidance issued by the Financial Accounting Standards Board (FASB). The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Principles of Consolidation	Principles of Consolidation : The consolidated financial statements include the results of Torchmark and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. When Torchmark acquires a subsidiary or a block of business, the assets acquired and the liabilities assumed are measured at fair value at the acquisition date. Any excess of acquisition cost over the fair value of net assets is recorded as goodwill. Expenses incurred to effect the acquisition are charged to earnings as of the acquisition date. Upon acquisition, the accounts and results of operations are consolidated as of and subsequent to the acquisition date. Torchmark accounts for its variable interest entities (VIEs) under accounting guidance which clarifies the definition of a variable interest and the instructions for consolidating VIEs. Only primary beneficiaries are required or allowed to consolidate VIEs. Therefore, a company may have voting control of a VIE, but if it is not the primary beneficiary, it is not permitted to consolidate the VIE. As further described under the caption Low-Income Housing Tax Credit Interests below in this note, Torchmark holds passive interests in limited partnerships which provide investment returns through the provision of tax benefits (principally from the transfer of federal or state tax credits related to federal low-income housing). These interests are considered to be VIEs. They are not consolidated because the Company has no power to control the activities that most significantly affect the economic performance of these entities and therefore the Company is not the primary beneficiary of any of these interests. Torchmark’s involvement is limited to its limited partnership interest in the entities. Torchmark has not provided any other financial support to the entities beyond its commitments to fund its limited partnership interests, and there are no arrangements or agreements with any of the interests to provide other financial support. The maximum loss exposure relative to these interests is limited to their carrying value.
Investments	Investments : Torchmark classifies all of its fixed maturity investments, which include bonds and redeemable preferred stocks, as available for sale. Investments classified as available for sale are carried at fair value with unrealized gains and losses, net of deferred taxes, reflected directly in accumulated other comprehensive income. Policy loans are carried at unpaid principal balances. Other long-term investments include equity securities, real estate, mortgage participations, and limited partnerships. Investments in equity securities, which include common and nonredeemable preferred stocks, are reported at fair value with unrealized gains and losses, net of deferred taxes, reflected directly in accumulated other comprehensive income. Investments in real estate are reported at cost less allowances for depreciation. Depreciation is calculated on the straight-line method. Mortgage participations, a type of investment where the mortgage loan is shared among investors, are accounted for as financing receivables. Investments in limited partnerships are primarily accounted for using the cost method of accounting as Torchmark's partnership interest is minor as Torchmark lacks the ability to exercise significant influence over the partnership's operating and financial policies. The Company considers its cost method investments for impairment when the carrying value of such investments exceeds the net asset value (“NAV”). As further discussed below in Accounting Pronouncements Not Yet Adopted , the Company will adopt ASU 2016-01 on January 1, 2018 which removes the cost method for certain investments and replaces it with fair value through net income method. Under the new guidance, limited partnerships will be reported at fair value and all fluctuations in fair value will be reported through realized gains and losses. Short-term investments include investments in interest-bearing assets with original maturities of twelve months or less. Gains and losses realized on the disposition of investments are determined on a specific identification basis.
Impairment of Investments	Impairment of Investments : Torchmark’s portfolio of fixed maturities fluctuates in value due to changes in interest rates in the financial markets as well as other factors. Fluctuations caused by market interest rate changes have little bearing on whether or not the investment will be ultimately recoverable. Therefore, Torchmark considers these declines in value resulting from changes in market interest rates to be temporary. In certain circumstances, however, Torchmark determines that the decline in the value of a security is other-than-temporary and writes the book value of the security down to its fair value, realizing an investment loss. The evaluation of Torchmark’s securities for other-than-temporary impairments is a process that is undertaken at least quarterly and is overseen by a team of investment and accounting professionals. Each security, which is impaired because the fair value is less than the cost or amortized cost, is identified and evaluated. The determination that an impairment is other-than-temporary is highly subjective and involves the careful consideration of many factors. Among the factors considered are: • The length of time and extent to which the security has been impaired • The reason(s) for the impairment • The financial condition of the issuer and the prospects for recovery in fair value of the security • The Company’s ability and intent to hold the security until anticipated recovery • Expected future cash flows The relative weight given to each of these factors can change over time as facts and circumstances change. In many cases, management believes it is appropriate to give relatively more weight to prospective factors than to retrospective factors. Prospective factors that are given more weight include prospects for recovery, the Company’s ability and intent to hold the security until anticipated recovery, and expected future cash flows. Among the facts and information considered in the process are: • Financial statements of the issuer • Changes in credit ratings of the issuer • The value of underlying collateral • News and information included in press releases issued by the issuer • News and information reported in the media concerning the issuer • News and information published by or otherwise provided by credit analysts • The nature and amount of recent and expected future sources and uses of cash • Default on a required payment • Issuer bankruptcy filings While all available information is taken into account, it is difficult to predict the ultimate recoverable amount of a distressed or impaired security. If a security is determined to be other-than-temporarily impaired, the cost basis of the security is written down to fair value and is treated as a realized loss in the period the determination is made. The written-down security will be amortized and revenue recognized in accordance with estimated future cash flows. Current accounting guidance is such that if an entity intends to sell or if it is more likely than not that it will be required to sell an impaired security prior to recovery of its cost basis, the security is to be considered other-than-temporarily impaired and the full amount of impairment must be charged to earnings. Otherwise, losses on fixed maturities which are other-than-temporarily impaired are separated into two categories, the portion of loss which is considered credit loss and the portion of loss which is due to other factors. The credit loss portion is charged to earnings while the loss due to other factors is charged to other comprehensive income. The credit loss portion of an impairment is determined as the difference between the security’s amortized cost and the present value of expected future cash flows discounted at the security’s original effective yield rate. The temporary portion is the difference between this present value of expected future cash flows and fair value (as discounted by a market yield). The expected cash flows are determined using judgment and the best information available to the Company. Inputs used to derive expected cash flows include expected default rates, current levels of subordination, and loan-to-collateral value ratios.
Cash	Cash : Cash consists of balances on hand and on deposit in banks and financial institutions.
Accrued Investment Income and Other Receivables	Accrued investment income : Accrued investment income consists of interest income or dividends earned on the investment portfolio, but are yet to be received as of the balance sheet date. Other Receivables : Other receivables consist mostly of agent debit balances, which primarily represent commissions advanced to insurance agents. These balances are repaid to the Company over time as the premiums associated with the advanced commissions are collected by the Company and the agents' commissions on such premiums are retained.
Deferred Acquisition Costs	Deferred Acquisition Costs : Certain costs of acquiring new insurance business are deferred and recorded as an asset. These costs are essential for the acquisition of new insurance business and are directly related to the successful issuance of an insurance contract including sales commissions, policy issue costs, and underwriting costs. Additionally, deferred acquisition costs (DAC) include the value of business acquired (VOBA), which are the costs of acquiring blocks of insurance from other companies or through the acquisition of other companies. These costs represent the difference between the fair value of the contractual insurance assets acquired and liabilities assumed compared against the assets and liabilities for insurance contracts that the Company issues or holds measured in accordance with GAAP. DAC and VOBA are amortized in a systematic manner which matches these costs with the associated revenues. Policies other than universal life-type policies are amortized with interest over the estimated premium-paying period of the policies in a manner which charges each year’s operations in proportion to the receipt of premium income. Universal life-type policies are amortized with interest in proportion to estimated gross profits. The assumptions used to amortize acquisition costs with regard to interest, mortality, morbidity, and persistency are consistent with those used to estimate the liability for future policy benefits. For interest-sensitive and deposit-balance type products, these assumptions are reviewed on a regular basis and are revised if actual experience differs significantly from original expectations. For all other products, amortization assumptions are generally not revised once established. DAC are subject to periodic recoverability and loss recognition testing to determine if there is a premium deficiency. These tests evaluate whether the present value of future contract-related cash flows will support the capitalized DAC asset. These cash flows consist primarily of premium income, less benefits and expenses taking inflation into account. The present value of these cash flows, less the benefit reserve, is then compared with the unamortized deferred acquisition cost balance. In the event the estimated present value of net cash flows is less, the deficiency would be recognized by a charge to earnings and either a reduction of unamortized acquisition costs or an increase in the liability for future benefits, as described under the caption Future Policy Benefits .
Advertising Costs	Advertising Costs : Costs related to advertising are generally charged to expense as incurred. However, certain Globe Life Direct Response advertising costs are capitalized when there is a reliable and demonstrated relationship between total costs and future benefits that is a direct result of incurring these costs. Globe Life Direct Response advertising costs consist primarily of the production and distribution costs of direct mail advertising materials, and when capitalized are included as a component of DAC. They are amortized in the same manner as other DAC.
Goodwill	Goodwill : The excess cost of a business acquired over the fair value of net assets acquired is reported as goodwill. Goodwill is subject to impairment testing in accordance with GAAP on an annual basis, or whenever potential impairment triggers occur. The Company may perform a qualitative analysis under certain circumstances, or perform a two-step quantitative analysis. In the qualitative analysis, the Company determines if it is more likely than not that the fair value of a reporting unit is less than its carrying amount by assessing current events and circumstances. If there are factors present indicating potential impairment, the Company would proceed to the two-step quantitative analysis. In the two-step quantitative analysis, the Company utilizes two approaches, income and market, to determine the fair value of each reporting unit. In the income approach, judgment and assumptions are used in developing the projected cash flows for the reporting units, and such estimates are subject to change. The Company also exercises judgment in the determination of the discount rate as management believes this to be appropriate for the risk associated with the cash flow expectations. In the market approach, the Company utilizes the share price and a control premium based on businesses with similar assets to determine a fair value. In both cases, the fair value of each reporting unit is then measured against that reporting unit’s corresponding carrying value. In the event the fair value is less than the carrying value, further testing is required under the accounting guidance to determine the amount of impairment, if any. If there is an impairment in the goodwill of any reporting unit, it is written down and charged to earnings in the period of the test.
Low-Income Housing Tax Credit Interests	Low-Income Housing Tax Credit Interests : Torchmark invests in limited partnerships that provide low-income housing tax credits and other related federal income tax benefits to Torchmark. The carrying value of Torchmark’s investment in these entities was $228 million and $280 million at December 31, 2017 and 2016 , respectively and was included in "Other assets" on the Consolidated Balance Sheets. As of December 31, 2017 , Torchmark was obligated under future commitments of $34 million , which are recorded in "Other liabilities". For guaranteed investments acquired prior to January 1, 2015, the Company utilizes the effective-yield method of amortization while the proportional method of amortization is utilized for all non-guaranteed as well as guaranteed investments acquired on or after January 1, 2015. All amortization expense is recorded in "Income tax benefit (expense)" on the Consolidated Statements of Operations .
Property and Equipment	Property and Equipment : Property and equipment, included in “Other assets,” is reported at cost less allowances for depreciation. Depreciation is recorded primarily on the straight line method over the estimated useful lives of these assets which range from three to five years for equipment and ten to forty years for buildings and improvements. Ordinary maintenance and repairs are charged to income as incurred. Impairments, if any, are recorded when certain events and circumstances become evident that the fair value of the asset is less than its carrying amount.
Future Policy Benefits	Future Policy Benefits : The liability for future policy benefits for annuity and universal life-type products is represented by policy account value. The liability for future policy benefits for all other life and health products, approximately 87% of total future policy benefits, is determined on the net level premium method. This method provides for the present value of expected future benefit payments less the present value of expected future net premiums, based on estimated investment yields, mortality, morbidity, persistency and other assumptions which were considered appropriate at the time the policies were issued. For limited-payment contracts, a deferred profit liability is also recorded which causes profits to emerge over the life of the contract in proportion to policies in force. Assumptions used for traditional life and health insurance products are based primarily on Company experience. Assumptions for interest rates range from 2.5% to 7.0% for Torchmark’s insurance companies with an overall weighted average assumed rate of 5.80% . Mortality tables used for individual life insurance include various statutory tables and modifications of a variety of generally accepted actuarial tables. Morbidity assumptions for individual health are based on Company experience and industry data. Withdrawal and termination assumptions are based on Torchmark’s experience. Once established, assumptions for these products are generally not changed. An additional provision is made on most products to allow for possible adverse deviation from the assumptions. These estimates are reviewed annually and compared with actual experience. If it is determined that existing contract liabilities, together with the present value of future gross premiums, will not be sufficient to cover the present value of future benefits and to recover unamortized deferred acquisition costs, then a premium deficiency exists. Such a deficiency would be recognized immediately by a charge to earnings and either a reduction of unamortized deferred acquisition costs or an increase in the liability for future policy benefits. From that point forward, the liability for future policy benefits would be based on revised assumptions.
Policy Claims and Other Benefits Payable	Policy Claims and Other Benefits Payable : Torchmark establishes a liability for known policy benefits payable and an estimate of claims that have been incurred but not yet reported to the Company. Torchmark makes an estimate of unreported claims after careful evaluation of all information available to the Company. This estimate is based on prior experience and is reviewed quarterly. However, there is no certainty the stated liability for claims and other benefits, including the estimate of unsubmitted claims, will be Torchmark’s ultimate obligation.
Income Taxes	Income Taxes : Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement book values and tax bases of assets and liabilities. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. On December 22, 2017, the Tax Cuts and Jobs Act (Tax Legislation) was enacted into law which changed existing tax law, including a reduction of the corporate income tax rate from 35% to 21% effective January 1, 2018. The Company recorded $877 million of tax benefits in net income in 2017 as a result of re-measuring its deferred assets and liabilities using the lower corporate tax rate as of the date of enactment. Based on the analysis of the Tax Legislation, the Company was able to determine that this amount is a reasonable estimate of the impact of the Tax Legislation in accordance with SEC Staff Accounting Bulletin (SAB) No. 118. However, the Company will continue to analyze relevant information to complete the accounting for income taxes which may result in an adjustment to tax expense in 2018. The accounting is expected to be complete when the 2017 U.S. corporate income tax returns are filed later in 2018. More information concerning income taxes is provided in Note 8—Income Taxes .
Postretirement Benefits	Postretirement Benefits : Torchmark accounts for its postretirement defined benefit plans by recognizing the funded status of those plans on its Consolidated Balance Sheets in accordance with accounting guidance. Periodic gains and losses attributable to changes in plan assets and liabilities that are not recognized as components of net periodic benefit costs are recognized as components of other comprehensive income, net of tax.
Treasury Stock	Treasury Stock : Torchmark accounts for purchases of treasury stock on the cost method. Issuance of treasury stock is accounted for using the weighted-average cost method.
Recognition of Premium Revenue and Related Expenses	Recognition of Premium Revenue and Related Expenses : Premium income for traditional long-duration life and health insurance products is recognized evenly over the contract period and when due from the policyholder. Premiums for short-duration health contracts are recognized as revenue over the contract period in proportion to the insurance protection provided. Premiums for universal life-type and annuity contracts are added to the policy account value, and revenues for such products are recognized as charges to the policy account value for mortality, administration, and surrenders (retrospective deposit method). Life premium includes policy charges of $17 million , $18 million , and $19 million for the years ended December 31, 2017 , 2016 , and 2015 , respectively. Other premium consists of annuity policy charges in each year. For most insurance products, the related benefits and expenses are matched with revenues by means of the provision of future policy benefits and the amortization of DAC in a manner which recognizes profits as they are earned over the revenue recognition period. For limited-payment life insurance products, the profits are recognized over the contract period.
Stock-Based Compensation	Stock-Based Compensation : Torchmark accounts for stock-based compensation by recognizing an expense in the financial statements based on the “fair value method.” The fair value method requires that a fair value be assigned to a stock option or other stock grant on its grant date and that this value be amortized over the grantees’ service period. The fair value method requires the use of an option valuation model to value employee stock options. Torchmark has elected to use the Black-Scholes valuation model for option expensing. A summary of assumptions for options granted in each of the three years 2015 through 2017 is as follows: 2017 2016 2015 Volatility factor 14.8 % 19.2 % 23.6 % Dividend yield 0.7 % 1.1 % 0.9 % Expected term (in years) 5.71 5.78 5.66 Risk-free rate 2.0 % 1.3 % 1.6 % The expected term is generally derived from Company experience. However, expected terms are determined based on the simplified method as permitted under the ASC 718 Stock Compensation topic when Company experience is insufficient. The Torchmark Corporation 2011 Incentive Plan replaced all previous plans and allows for option grants for employees with a ten -year contractual term which vest over five years in addition to seven -year grants which vest over three years as permitted by the previous plans. Director grants vest over six months. The Company has sufficient experience with seven -year grants that vest in three years, but insufficient historical experience with five -year vesting. Therefore, Torchmark has used the simplified method to determine the expected term for the ten -year grants with five -year vesting and will do so until adequate experience is developed. Volatility and risk-free interest rates are assumed over a period of time consistent with the expected term of the option. Volatility is measured on a historical basis. Monthly data points are utilized to derive volatility for periods greater than three years. Expected dividend yield is based on current dividend yield held constant over the expected term. Once the fair value of an option has been determined, it is amortized on a straight-line basis over the employee’s service period for that grant (from the grant date to the date the grant is fully vested). Expenses for restricted stock and restricted stock units are based on the grant date fair value allocated on a straight-line basis over the service period. Performance share expense is recognized based on management’s estimate of the probability of meeting the metrics identified in the performance share award agreement, assigned to each service period as these estimates develop. Torchmark management views all stock-based compensation expense as a corporate or Parent Company expense and, therefore, presents it as such in its segment analysis (See Note 14—Business Segments ). It is included in “Other operating expense” in the Consolidated Statements of Operations .
Earnings Per Share	Earnings Per Share : Torchmark presents basic and diluted earnings per common share (EPS) on the face of the Consolidated Statements of Operations for income from continuing operations and income from discontinued operations. Basic EPS is computed by dividing income available to common shareholders by the weighted average common shares outstanding for the period. Diluted EPS is calculated by adding to shares outstanding the additional net effect of potentially dilutive securities or contracts, such as stock options, which could be exercised or converted into common shares.
Accounting Pronouncements Adopted In Current Year / Not Yet Adopted	Accounting Pronouncements Adopted in the Current Year : ASU 2018-02 : In February 2018, the FASB issued ASU No. 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (AOCI) . This guidance was issued to allow the reclassification of taxes from AOCI to retained earnings as a result of the reduction in corporate income tax rates due to Tax Legislation. Current accounting requires the effect of changes in tax rates used to measure deferred tax assets and liabilities to be reported in net income as of the date of enactment even though deferred taxes were previously recognized in AOCI (stranded taxes). This guidance, however, allows a company to elect to reclassify the stranded taxes in AOCI to retained earnings and is effective for years beginning after December 15, 2018, with early adoption permitted. The Company elected to early adopt this guidance resulting in a reclassification of $252 million from AOCI to retained earnings for the period ended December 31, 2017. See Consolidated Statements of Shareholders' Equity and Note 3—Supplemental Information about Changes to Accumulated Other Comprehensive Income . Accounting Pronouncements Not Yet Adopted : ASU 2016-01: In January 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-01, Financial Instruments—Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities, which primarily revises the classification and measurement of certain equity investments such that they will be measured at fair value through net income. Additionally, it eliminates the cost method for partnerships and joint ventures and requires these types of investments to be accounted for under the fair value through net income method or equity method. Lastly, the guidance will require certain disclosures associated with fair value of financial instruments. This standard became effective for the Company on January 1, 2018. The adoption will result in a $6 million positive adjustment to the opening balance of retained earnings as we have minimal ownership interests in equity investments and partnerships. ASU 2016-02: In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which requires all lessees to report a right-of-use asset and a lease liability for leases with a term life greater than 12 months. Operating and financing leases will be recognized on the balance sheet going forward. Additional qualitative and quantitative disclosures will be required. This standard will become effective for the Company beginning January 1, 2019 and will require recognizing and measuring leases at the beginning of the earliest period presented using a modified retrospective approach. Early adoption is permitted. The Company does not expect the adoption to have a significant impact on the financial statements. Refer to Note 15—Commitments and Contingencies for consideration of the noncancelable operating lease commitments. The Company is not a lessor. ASU 2016-13: In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments as well as to change the loss impairment methodology for available-for-sale debt securities by use of an allowance rather than a direct write-down. This standard will become effective on January 1, 2020. The applicable section of the standard related to debt securities requires a prospective transition. The Company does not expect the adoption to have a significant impact on the financial statements as we have limited credit losses with respect to our available-for-sale portfolio. ASU 2016-15: In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments to provide uniformity in the classification of cash receipts and payments recorded in the statement of cash flows including debt prepayment or debt extinguishment costs, settlement of zero-coupon bonds, and proceeds from the settlement of insurance claims. This standard became effective on January 1, 2018 and will not have a significant impact to the classification on our Statement of Cash Flows . ASU 2016-16: In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfer of Assets Other Than Inventory. This guidance was issued to improve the accounting for income tax consequences of intra-entity transfers of assets other than inventory by allowing the immediate recognition of the current and deferred income tax effects. Current guidance prohibits the recognition of current and deferred income taxes for an intra-entity transfer until the asset has been sold to an outside party. This new guidance should be applied on a modified retrospective approach and became effective on January 1, 2018. This adoption will not have a significant impact on the financial statements. ASU 2017-04: In January 2017, the FASB issued ASU No. 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. This guidance was issued to simplify the subsequent measurement of goodwill through the elimination of Step 2 from the goodwill impairment test which required a hypothetical purchase price allocation. It will become effective on January 1, 2020 and should be applied on a prospective basis. This adoption will not have an impact to the financial statements. ASU 2017-07: In March 2017, the FASB issued ASU No. 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. This guidance was issued to simplify the reporting of pension costs by disaggregating the service-cost component from the other components of net benefit costs and reporting it separately on the income statement. The service-cost component is the only component of net benefit cost that will be eligible for capitalization. The guidance became effective on January 1, 2018 with a retrospective transition method for separation of net benefit costs and a prospective transition method for the capitalization of service costs. The Company expects the adoption to add an additional $3 to $5 million in expense to the 2018 Consolidated Statements of Operations due to the elimination of the ability to capitalize a portion of the benefit costs. ASU 2017-08: In March 2017, the FASB issued ASU No. 2017-08, Receivables—Nonrefundable Fees and Other Costs (Topic 310-20): Premium Amortization on Purchased Callable Debt Securities. This guidance was issued to shorten the amortization period for certain callable debt securities held at a premium. The guidance requires the premium to be amortized to the earliest call date. It will become effective on January 1, 2019 with early adoption permitted, including during interim periods. The adoption is to be applied on a modified retrospective basis through an adjustment to retained earnings. This adoption will not have a significant impact on the financial statements. ASU 2017-09: In May 2017, the FASB issued ASU No. 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting. This guidance was issued to provide clarity and guidance regarding changes to the terms or conditions of a share-based payment award that requires an entity to apply modification accounting. It became effective on January 1, 2018 with early adoption permitted, including adoption in any interim periods. The adoption will have a minimal impact on the financial statements as modifications to stock compensation are infrequent.
Fair Value Measurements, Investments in Securities
Significant Accounting Policies [Line Items]
Fair Value Measurements	Fair Value Measurements, Investments in Securities : Torchmark measures the fair value of its fixed maturities based on a hierarchy consisting of three levels which indicate the quality of the fair value measurements as described below: • Level 1— fair values are based on quoted prices in active markets for identical assets or liabilities that the Company has the ability to access as of the measurement date. • Level 2 — fair values are based on inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability, or inputs that can otherwise be corroborated by observable market data. • Level 3— fair values are based on inputs that are considered unobservable where there is little, if any, market activity for the asset or liability as of the measurement date. In this circumstance, the Company has to rely on values derived by independent brokers or internally-developed assumptions. Unobservable inputs are developed based on the best information available to the Company which may include the Company’s own data or bid and ask prices in the dealer market. The great majority of Torchmark's fixed maturities are not actively traded and direct quotes are not generally available. Management therefore determines the fair values of these securities after consideration of data provided by third-party pricing services, independent broker/dealers, and other resources. At December 31, 2017 , Torchmark's investments in fixed maturities were primarily composed of the following significant security types: Corporate securities, state and municipal securities, redeemable preferred stocks, and U.S. government securities. The remaining security types represented less than 1% of the total in the aggregate. Over 95% of the fair value reported at December 31, 2017 was determined using data provided by third-party pricing services. Prices provided by these services are not binding offers, but are estimated exit values. Third-party pricing services use proprietary pricing models to determine security values by discounting cash flows using a market-adjusted spread to a benchmark yield. For all asset classes within Torchmark’s significant security types, third-party pricing services use a common valuation technique to model the price of the investments using observable market data. The foundation for these models consists of developing yield spreads based on multiple observable market inputs, including but not limited to: benchmark yield curves, actual trading activity, new issue yields, broker-dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, sector-specific data, economic data, and other inputs that are corroborated in the market. Pricing vendors monitor and review their pricing data continuously with current market and economic data feeds, augmented by ongoing communication within the dealer community. Using the observable market inputs described above, spreads to an appropriate benchmark yield are further developed by the vendors for each security based on security-specific and/or sector-specific risk factors, such as a security’s terms and conditions (coupon, maturity, and call features), credit rating, sector, liquidity, collateral or other cash flow options, and other factors that could impact the risk of the security. Embedded repayment options, such as call and redemption features, are also taken into account in the pricing models. When the spread is determined, it is added to the security’s benchmark yield. The security's expected cash flows are discounted using this spread-adjusted yield, and the resulting present value of the discounted cash flows is the evaluated price. When third-party vendor prices are not available, the Company attempts to obtain valuations from other sources, including but not limited to broker/dealers, broker quotes, and prices on comparable securities. When valuations have been obtained for all securities in the portfolio, management reviews and analyzes the prices to ensure their reasonableness, taking into account available observable information. When two or more valuations are available for a security and the variance between the prices is 10% or less, the close correlation suggests similar observable inputs were used in deriving the price, and the mean of the prices is used. Securities valued in this manner are classified as Level 2. When the variance between two or more valuations for a security exceeds 10%, additional analysis is performed to determine the most appropriate value for that security, using resources such as broker quotes, prices on comparable securities, recent trades, and any other observable market data. Further review is performed on the available valuations to determine if they can be corroborated within reasonable tolerance to any other observable evidence. If one of the valuations or the mean of the available valuations for a security can be corroborated with other observable evidence, then the corroborated value is used and reported as Level 2. The Company uses information and analytical techniques deemed appropriate for determining the point within the range of reasonable fair value estimates that is most representative of fair value under current market conditions. Valuations that cannot be corroborated within a reasonable tolerance are classified as Level 3. Torchmark invests in a portfolio of private placement bonds which are not actively traded. This portfolio is managed by third parties. The portfolio managers provide valuations for the bonds based on a pricing matrix utilizing observable inputs, such as the benchmark treasury rate and published sector indices, and unobservable inputs such as an internally-developed credit rating. If they cannot be corroborated, the fair values are classified as Level 3.
Fair Value Measurements, Other Financial Instruments
Significant Accounting Policies [Line Items]
Fair Value Measurements	Fair Value Measurements, Other Financial Instruments : Fair values for cash, short-term investments, short-term debt, mortgage participations, receivables and payables approximate carrying value. Policy loans are an integral part of Torchmark’s subsidiaries’ life insurance policies in force and their fair values cannot be valued separately and apart from the insurance contracts. The fair values of Torchmark’s long-term debt issues are based on the same methodology as investments in fixed maturities. At December 31, 2017 , observable inputs were available for these debt securities and as such were classified as Level 2 in the valuation hierarchy. The fair value for each debt instrument as of December 31, 2017 is disclosed in Note 11—Debt . As described in Note 9—Postretirement Benefits , Torchmark maintains a nonqualified supplemental retirement plan. Therefore the assets which support the liability for this plan are considered general assets of the Company. These assets consist of the cash value of corporate-owned life insurance policies (COLI) and exchange traded funds (ETFs). The fair value of the insurance cash values approximates carrying value. Fair values for the ETFs are derived from direct quotes and are considered Level 1 in the valuation hierarchy.

Significant Accounting Polici28

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Assumptions for Options Granted	A summary of assumptions for options granted in each of the three years 2015 through 2017 is as follows: 2017 2016 2015 Volatility factor 14.8 % 19.2 % 23.6 % Dividend yield 0.7 % 1.1 % 0.9 % Expected term (in years) 5.71 5.78 5.66 Risk-free rate 2.0 % 1.3 % 1.6 %

Statutory Accounting (Tables)

Statutory Accounting (Tables)	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Consolidated Net Income and Shareholders' Equity for Insurance Companies	Consolidated net income and shareholders’ equity (capital and surplus) on a statutory basis for the insurance subsidiaries were as follows: Net Income Shareholders’ Equity Year Ended December 31, At December 31, 2017 2016 2015 2017 2016 Life insurance subsidiaries $ 426,285 $ 429,563 $ 393,466 $ 1,254,875 $ 1,335,070

Supplemental Information Abou30

Supplemental Information About Changes to Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Change in Balance by Component of Accumulated Other Comprehensive Income	An analysis in the change in balance by component of Accumulated Other Comprehensive Income is as follows for each of the years 2015 through 2017 . Components of Accumulated Other Comprehensive Income For the 12 months ended December 31, 2015: Available Deferred Foreign Pension Total Balance at January 1, 2015 $ 1,090,273 $ (10,758 ) $ 17,386 $ (99,449 ) $ 997,452 Other comprehensive income (loss) before reclassifications, net of tax (759,976 ) 5,643 (13,759 ) (8,930 ) (777,022 ) Reclassifications, net of tax 2,036 — — 9,481 11,517 Other comprehensive income (loss) (757,940 ) 5,643 (13,759 ) 551 (765,505 ) Balance at December 31, 2015 332,333 (5,115 ) 3,627 (98,898 ) 231,947 For the 12 months ended December 31, 2016: Other comprehensive income (loss) before reclassifications, net of tax 356,016 (1,567 ) 1,340 (20,736 ) 335,053 Reclassifications, net of tax 3,965 — — 6,609 10,574 Other comprehensive income (loss) 359,981 (1,567 ) 1,340 (14,127 ) 345,627 Balance at December 31, 2016 692,314 (6,682 ) 4,967 (113,025 ) 577,574 For the 12 months ended December 31, 2017: Other comprehensive income (loss) before reclassifications, net of tax 621,619 (350 ) 8,452 (20,753 ) 608,968 Reclassifications, net of tax (22,751 ) — — 8,083 (14,668 ) Other comprehensive income (loss) 598,868 (350 ) 8,452 (12,670 ) 594,300 Reclassifications, Tax reform (1) 278,107 (1,515 ) 2,883 (27,075 ) 252,400 Balance at December 31, 2017 $ 1,569,289 $ (8,547 ) $ 16,302 $ (152,770 ) $ 1,424,274 (1) Income tax effects of certain items were reclassified from accumulated other comprehensive income to retained earnings to remove stranded tax effects as a result of early adoption of ASU No. 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . See further discussion in Note 1—Significant Accounting Policies .
Summary of Reclassifications Out of Accumulated Other Comprehensive Income	Reclassification adjustments out of Accumulated Other Comprehensive Income are presented below for each of the years 2015 through 2017 . Reclassification Adjustments Year Ended December 31, Component Line Item 2017 2016 2015 Affected line items in the Unrealized gains (losses) on available for sale assets: Realized (gains) losses $ (34,954 ) $ 10,285 $ 9,478 Realized investment gains (losses) Amortization of (discount) premium (47 ) (4,185 ) (6,346 ) Net investment income Total before tax (35,001 ) 6,100 3,132 Tax 12,250 (2,135 ) (1,096 ) Income taxes Total after tax (22,751 ) 3,965 2,036 Pension adjustments: Amortization of prior service cost 476 477 377 Other operating expenses Amortization of actuarial (gain) loss 11,960 9,691 14,209 Other operating expenses Total before tax 12,436 10,168 14,586 Tax (4,353 ) (3,559 ) (5,105 ) Income taxes Total after tax 8,083 6,609 9,481 Total reclassifications (after tax) $ (14,668 ) $ 10,574 $ 11,517

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Summary of Fixed Maturities and Equity Securities Available for Sale by Component	A summary of fixed maturities available for sale by cost or amortized cost and estimated fair value at December 31, 2017 and 2016 is as follows: 2017: Cost or Gross Gross Fair Value (1) % of Total (2) Fixed maturities available for sale: U.S. Government direct, guaranteed, and government-sponsored enterprises $ 390,646 $ 18,173 $ (1,373 ) $ 407,446 2 States, municipalities, and political subdivisions 1,091,960 127,890 (135 ) 1,219,715 7 Foreign governments 20,236 1,782 — 22,018 — Corporates, by sector: Financial 3,282,526 475,961 (23,392 ) 3,735,095 22 Utilities 1,955,737 369,406 (1,298 ) 2,323,845 14 Energy 1,619,349 226,140 (25,392 ) 1,820,097 11 Other corporate sectors 6,065,803 747,612 (20,616 ) 6,792,799 40 Total corporates 12,923,415 1,819,119 (70,698 ) 14,671,836 87 Collateralized debt obligations 59,150 20,084 (7,653 ) 71,581 — Other asset-backed securities 144,520 4,835 — 149,355 1 Redeemable preferred stocks, by sector: Financial 336,621 62,892 (2,727 ) 396,786 3 Utilities 28,553 2,132 (97 ) 30,588 — Total redeemable preferred stocks 365,174 65,024 (2,824 ) 427,374 3 Total fixed maturities $ 14,995,101 $ 2,056,907 $ (82,683 ) $ 16,969,325 100 (1) Amount reported in the balance sheet. (2) At fair value. 2016: Cost or Gross Gross Fair Value (1) % of Total (2) Fixed maturities available for sale: U.S. Government direct, guaranteed, and government-sponsored enterprises $ 381,054 $ 895 $ (9,151 ) $ 372,798 3 States, municipalities, and political subdivisions 1,284,605 126,850 (1,327 ) 1,410,128 9 Foreign governments 21,701 1,438 (62 ) 23,077 — Corporates, by sector: Financial 2,963,584 285,037 (45,885 ) 3,202,736 21 Utilities 1,875,946 249,701 (12,604 ) 2,113,043 14 Energy 1,542,426 127,989 (44,324 ) 1,626,091 11 Other corporate sectors 5,601,136 424,021 (84,547 ) 5,940,610 39 Total corporates 11,983,092 1,086,748 (187,360 ) 12,882,480 85 Collateralized debt obligations 60,726 13,062 (10,285 ) 63,503 — Other asset-backed securities 56,410 621 (337 ) 56,694 — Redeemable preferred stocks, by sector: Financial 371,862 43,383 (7,218 ) 408,027 3 Utilities 28,600 798 (244 ) 29,154 — Total redeemable preferred stocks 400,462 44,181 (7,462 ) 437,181 3 Total fixed maturities $ 14,188,050 $ 1,273,795 $ (215,984 ) $ 15,245,861 100 (1) Amount reported in the balance sheet. (2) At fair value.
Schedule of Fixed Maturities by Contractual Maturity	A schedule of fixed maturities available for sale by contractual maturity date at December 31, 2017 is shown below on an amortized cost basis and on a fair value basis. Actual maturity dates could differ from contractual maturities due to call or prepayment provisions. Amortized Fair Fixed maturities available for sale: Due in one year or less $ 147,457 $ 149,495 Due after one year through five years 682,932 720,186 Due after five years through ten years 1,397,473 1,567,972 Due after ten years through twenty years 4,701,591 5,519,917 Due after twenty years 7,861,000 8,789,769 Mortgage-backed and asset-backed securities 204,648 221,986 $ 14,995,101 $ 16,969,325
Schedule of Analysis of Investment Operations	Year Ended December 31, 2017 2016 2015 Net investment income is summarized as follows: Fixed maturities available for sale $ 817,213 $ 778,912 $ 747,663 Policy loans 39,578 38,436 36,763 Other long-term investments 4,991 2,786 2,021 Short-term investments 948 447 95 862,730 820,581 786,542 Less investment expense (14,845 ) (13,678 ) (12,591 ) Net investment income $ 847,885 $ 806,903 $ 773,951
Realized Gain (Loss) on Investments	An analysis of realized gains (losses) from investments is as follows: Realized investment gains (losses): Fixed maturities available for sale: Sales and other $ 35,199 $ (10,645 ) $ (9,479 ) Other-than-temporary impairments (245 ) — — Other investments (7,302 ) (38 ) 688 Loss on redemption on debt (4,041 ) — — 23,611 (10,683 ) (8,791 ) Applicable tax (6,021 ) 3,739 3,077 Realized gains (losses) from investments, net of tax $ 17,590 $ (6,944 ) $ (5,714 )
Unrealized Gain (Loss) on Investments	An analysis of the net change in unrealized investment gains (losses) is as follows: Fixed maturities available for sale $ 916,413 $ 551,658 $ (1,163,295 ) Other investments 5,008 2,143 (2,737 ) Net change in unrealized gains (losses) $ 921,421 $ 553,801 $ (1,166,032 )
Schedule of Selected Information about Sales of Fixed Maturities	Additional information about securities sold is as follows: At December 31, 2017 2016 2015 Fixed maturities available for sale: Proceeds from sales (1) $ 67,246 $ 358,285 $ 226,792 Gross realized gains 5,079 6,133 259 Gross realized losses (1,100 ) (32,608 ) (16,894 ) (1) Includes unsettled sales of $17.9 million at December 31, 2016 . There were no unsettled sales in 2017 or 2015.
Assets Measured at Fair Value on Recurring Basis	The following tables represent the fair value of fixed maturities measured on a recurring basis at December 31, 2017 and 2016 : Fair Value Measurements at December 31, 2017 Using: Description Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value Fixed maturities available for sale: U.S. Government direct, guaranteed, and government-sponsored enterprises $ — $ 407,446 $ — $ 407,446 States, municipalities, and political subdivisions 44 1,219,671 — 1,219,715 Foreign governments — 22,018 — 22,018 Corporates, by sector: Financial — 3,673,089 62,006 3,735,095 Utilities — 2,168,115 155,730 2,323,845 Energy — 1,779,281 40,816 1,820,097 Other corporate sectors — 6,468,541 324,258 6,792,799 Total corporates — 14,089,026 582,810 14,671,836 Collateralized debt obligations — — 71,581 71,581 Other asset-backed securities — 135,306 14,049 149,355 Redeemable preferred stocks, by sector: Financial — 396,786 — 396,786 Utilities — 30,588 — 30,588 Total redeemable preferred stocks — 427,374 — 427,374 Total fixed maturities $ 44 $ 16,300,841 $ 668,440 $ 16,969,325 Percentage of total — % 96.1 % 3.9 % 100.0 % Fair Value Measurements at December 31, 2016 Using: Description Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Fair Value Fixed maturities available for sale: U.S. Government direct, guaranteed, and government-sponsored enterprises $ — $ 372,798 $ — $ 372,798 States, municipalities, and political subdivisions 45,302 1,364,826 — 1,410,128 Foreign governments — 23,077 — 23,077 Corporates, by sector: Financial — 3,141,611 61,125 3,202,736 Utilities — 1,959,143 153,900 2,113,043 Energy — 1,598,976 27,115 1,626,091 Other corporate sectors — 5,623,150 317,460 5,940,610 Total corporates — 12,322,880 559,600 12,882,480 Collateralized debt obligations — — 63,503 63,503 Other asset-backed securities — 56,694 — 56,694 Redeemable preferred stocks, by sector: Financial — 408,027 — 408,027 Utilities — 29,154 — 29,154 Total redeemable preferred stocks — 437,181 — 437,181 Total fixed maturities $ 45,302 $ 14,577,456 $ 623,103 $ 15,245,861 Percentage of total 0.3 % 95.6 % 4.1 % 100.0 %
Schedule of Changes in Assets Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs	The following table represents changes in fixed maturities measured at fair value on a recurring basis using significant unobservable inputs (Level 3). Analysis of Changes in Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Asset- backed securities Collateralized debt Obligations Corporates Total Balance at January 1, 2015 $ — $ 63,232 $ 512,714 $ 575,946 Total gains or losses: Included in realized gains/losses — — 1,182 1,182 Included in other comprehensive income — 11,365 (11,925 ) (560 ) Acquisitions — — 38,600 38,600 Sales — — — — Amortization — 5,536 17 5,553 Other (1) — (9,751 ) (9,782 ) (19,533 ) Transfers into (out of) Level 3 (2) — — — — Balance at December 31, 2015 — 70,382 530,806 601,188 Total gains or losses: Included in realized gains/losses — — 788 788 Included in other comprehensive income — (3,943 ) 6,403 2,460 Acquisitions — — 33,662 33,662 Sales — — — — Amortization — 5,186 17 5,203 Other (1) — (8,122 ) (12,076 ) (20,198 ) Transfers into (out of) Level 3 (2) — — — — Balance at December 31, 2016 — 63,503 559,600 623,103 Total gains or losses: Included in realized gains/losses — — — — Included in other comprehensive income 410 9,654 10,900 20,964 Acquisitions 14,000 — 21,666 35,666 Sales — — — — Amortization — 4,914 17 4,931 Other (1) (361 ) (6,490 ) (9,373 ) (16,224 ) Transfers into (out of) Level 3 (2) — — — — Balance at December 31, 2017 $ 14,049 $ 71,581 $ 582,810 $ 668,440 (1) Includes foreign exchange adjustments and principal repayments. (2) There were no transfers in or out of Level 3 during the three years ended 2017 .
Quantitative Information about Level 3 Fair Value Measurements	Quantitative Information about Level 3 Fair Value Measurements As of December 31, 2017 Fair Value Valuation Significant Unobservable Range Weighted Asset-backed securities $ 14,049 Determination of credit spread Credit BBB BBB Discounted cash flows Discount 5.35% 5.35% Collateralized debt obligations 71,581 Discounted cash flows Discount 7.0 - 8.25% 8.03% Private placement fixed maturities $ 582,810 Determination of credit spread Credit A+ to BB- BBB Discounted cash flows Discount 2.97 - 7.27% 3.93% $ 668,440
Transfers in and Out of Each of the Valuation Levels of Fair Values	The following table presents transfers in and out of each of the valuation levels of fair values. 2017 2016 2015 In Out Net In Out Net In Out Net Level 1 $ 42,372 $ (597 ) $ 41,775 $ 45,344 $ — $ 45,344 $ 17,252 $ (49,744 ) $ (32,492 ) Level 2 597 (42,372 ) (41,775 ) — (45,344 ) (45,344 ) 49,744 (17,252 ) 32,492 Level 3 — — — — — — — — —
Schedule of Unrealized Investment Losses by Class of Investment	ANALYSIS OF GROSS UNREALIZED INVESTMENT LOSSES At December 31, 2017 Less than Twelve Months Twelve Months or Longer Total Description of Securities Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Fixed maturities available for sale: Investment grade securities: U.S. Government direct, guaranteed, and government-sponsored enterprises $ 34,388 $ (422 ) $ 47,514 $ (951 ) $ 81,902 $ (1,373 ) States, municipalities and political subdivisions 4,561 (21 ) 1,771 (9 ) 6,332 (30 ) Foreign governments — — — — — — Corporates, by sector: Financial 133,080 (652 ) 35,302 (1,429 ) 168,382 (2,081 ) Utilities 48,562 (569 ) 32,345 (729 ) 80,907 (1,298 ) Energy 23,463 (81 ) 67,775 (3,682 ) 91,238 (3,763 ) Metals and mining — — — — — — Other corporate sectors 220,661 (2,312 ) 163,886 (4,257 ) 384,547 (6,569 ) Total corporates 425,766 (3,614 ) 299,308 (10,097 ) 725,074 (13,711 ) Other asset-backed securities — — — — — — Redeemable preferred stocks, by sector: Utilities — — 5,953 (97 ) 5,953 (97 ) Total redeemable preferred stocks — — 5,953 (97 ) 5,953 (97 ) Total investment grade securities 464,715 (4,057 ) 354,546 (11,154 ) 819,261 (15,211 ) Below investment grade securities: States, municipalities and political subdivisions 200 (105 ) — — 200 (105 ) Corporates, by sector: Financial — — 84,432 (21,311 ) 84,432 (21,311 ) Energy 8,114 (104 ) 75,204 (21,525 ) 83,318 (21,629 ) Metals and mining — — — — — — Other corporate sectors 25,334 (5,066 ) 54,383 (8,981 ) 79,717 (14,047 ) Total corporates 33,448 (5,170 ) 214,019 (51,817 ) 247,467 (56,987 ) Collateralized debt obligations — — 12,347 (7,653 ) 12,347 (7,653 ) Redeemable preferred stocks, by sector: Financial — — 24,376 (2,727 ) 24,376 (2,727 ) Total redeemable preferred stocks — — 24,376 (2,727 ) 24,376 (2,727 ) Total below investment grade securities 33,648 (5,275 ) 250,742 (62,197 ) 284,390 (67,472 ) Total fixed maturities $ 498,363 $ (9,332 ) $ 605,288 $ (73,351 ) $ 1,103,651 $ (82,683 ) ANALYSIS OF GROSS UNREALIZED INVESTMENT LOSSES At December 31, 2016 Less than Twelve Months Twelve Months or Longer Total Description of Securities Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Fixed maturities available for sale: Investment grade securities: U.S. Government direct, guaranteed, and government-sponsored enterprises $ 321,133 $ (8,553 ) $ 1,404 $ (598 ) $ 322,537 $ (9,151 ) States, municipalities and political subdivisions 32,178 (1,114 ) 683 (19 ) 32,861 (1,133 ) Foreign governments 4,416 (62 ) — — 4,416 (62 ) Corporates, by sector: Financial 479,669 (18,666 ) 64,335 (4,627 ) 544,004 (23,293 ) Utilities 290,732 (11,000 ) 16,977 (1,604 ) 307,709 (12,604 ) Energy 83,064 (1,076 ) 154,908 (18,127 ) 237,972 (19,203 ) Metals and mining 5,936 (231 ) 5,789 (187 ) 11,725 (418 ) Other corporate sectors 1,564,273 (65,131 ) 68,968 (6,495 ) 1,633,241 (71,626 ) Total corporates 2,423,674 (96,104 ) 310,977 (31,040 ) 2,734,651 (127,144 ) Other asset-backed securities 41,498 (337 ) — — 41,498 (337 ) Redeemable preferred stocks, by sector: Utilities 5,857 (244 ) — — 5,857 (244 ) Total redeemable preferred stocks 5,857 (244 ) — — 5,857 (244 ) Total investment grade securities 2,828,756 (106,414 ) 313,064 (31,657 ) 3,141,820 (138,071 ) Below investment grade securities: States, municipalities and political subdivisions — — 357 (194 ) 357 (194 ) Corporates, by sector: Financial — — 83,174 (22,592 ) 83,174 (22,592 ) Energy 15,567 (385 ) 91,165 (24,736 ) 106,732 (25,121 ) Metals and mining 32,478 (172 ) 34,463 (2,023 ) 66,941 (2,195 ) Other corporate sectors 51,640 (291 ) 95,679 (10,017 ) 147,319 (10,308 ) Total corporates 99,685 (848 ) 304,481 (59,368 ) 404,166 (60,216 ) Collateralized debt obligations — — 9,714 (10,285 ) 9,714 (10,285 ) Redeemable preferred stocks, by sector: Financial — — 19,912 (7,218 ) 19,912 (7,218 ) Total redeemable preferred stocks — — 19,912 (7,218 ) 19,912 (7,218 ) Total below investment grade securities 99,685 (848 ) 334,464 (77,065 ) 434,149 (77,913 ) Total fixed maturities $ 2,928,441 $ (107,262 ) $ 647,528 $ (108,722 ) $ 3,575,969 $ (215,984 )
Schedule of Additional Information about Investments in Unrealized Loss Position	Additional information about fixed maturities available for sale in an unrealized loss position is as follows: Less than Twelve Total Number of issues (CUSIP numbers) held: As of December 31, 2017 92 102 194 As of December 31, 2016 407 94 501
Schedule of Other Long-Term Investments	Other long-term investments consist of the following: Year Ended December 31, 2017 2016 Investment in limited partnerships $ 66,522 $ 51,509 Commercial mortgage participations (1) 39,489 — Other 2,548 2,343 Total $ 108,559 $ 53,852 (1) A mortgage participation is a legal right to a prorata interest in a mortgage loan.
Schedule Of Percentages Of Investments By Major Components At Fair Value	At December 31, 2017 , the investment portfolio, at fair value, consisted of the following: Investment grade fixed maturities: Corporate securities 82 % Securities of state and municipal governments 7 Government-sponsored enterprises 2 Other 1 Below investment grade fixed maturities: Corporate securities 3 Other 1 Policy loans, which are secured by the underlying insurance policy values 3 Other investments 1 100 %
Schedule Of Industry Concentrations Held In Corporate Portfolio	Below are the ten largest industry concentrations held in the corporate portfolio of corporate debt securities and redeemable preferred stocks at December 31, 2017 , based on fair value: Insurance 16 % Electric utilities 12 Oil and natural gas pipelines 7 Banks 6 Transportation 4 Oil and natural gas exploration and production 4 Chemicals 4 Real estate investment trusts 4 Food 3 Metals and mining 3

Deferred Acquisition Costs (Tab

Deferred Acquisition Costs (Tables)	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Analysis of Deferred Acquisition Costs	An analysis of DAC is as follows: Year Ended December 31, 2017 2016 2015 Balance at beginning of year $ 3,783,158 $ 3,617,135 $ 3,457,397 Additions: Deferred during period: Commissions 465,920 436,252 401,166 Other expenses 194,214 199,066 211,015 Total deferred 660,134 635,318 612,181 Foreign exchange adjustment 5,712 2,180 — Adjustment attributable to unrealized investment losses (1) — — 8,682 Total additions 665,846 637,498 620,863 Deductions: Amortized during period (490,403 ) (469,063 ) (445,625 ) Foreign exchange adjustment — — (15,500 ) Adjustment attributable to unrealized investment gains (1) (538 ) (2,412 ) — Total deductions (490,941 ) (471,475 ) (461,125 ) Balance at end of year $ 3,958,063 $ 3,783,158 $ 3,617,135 (1) Represents amounts pertaining to investments relating to universal life-type products.

Discontinued Operations (Tables

Discontinued Operations (Tables)	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Disposal Groups, Including Discontinued Operations	The net assets related to discontinued operations at December 31, 2017 and 2016 were as follows: At December 31, 2017 2016 Assets: Due premiums $ 3,945 $ 8,840 Other receivables (1) 64,575 118,692 Total assets related to discontinued operations 68,520 127,532 Liabilities: Risk sharing payable 8,731 8,374 Current and deferred income taxes payable 1,077 3,820 Other (2) 40,046 15,230 Total liabilities related to discontinued operations 49,854 27,424 Net assets $ 18,666 $ 100,108 (1) At December 31, 2017 , other receivables included $65 million from Centers for Medicare and Medicaid Services (CMS). At December 31, 2016 , the comparable amounts were $50 million from CMS and $69 million from drug manufacturer rebates. (2) At December 31, 2017 , the balance included $37.3 million due to CMS. At December 31, 2016 , the balance includes $3.6 million contingent sale price reserve. Income from discontinued operations for the three years ended December 31, 2017 is as follows: Year Ended December 31, 2017 2016 2015 Revenue: Health premium $ — $ 222,840 $ 260,657 Benefits and expenses: Health policyholder benefits 3,827 183,423 213,114 Amortization of deferred acquisition costs — 3,747 3,506 Commissions, premium taxes, and non-deferred acquisition expenses 763 16,396 20,909 Other operating expense 1,209 5,377 6,502 Total benefits and expenses 5,799 208,943 244,031 Income before income taxes for discontinued operations (5,799 ) 13,897 16,626 Gain from sale of discontinued operations — 1,779 — Income taxes 2,030 (5,487 ) (5,819 ) Income from discontinued operations $ (3,769 ) $ 10,189 $ 10,807 Income taxes paid related to discontinued operations for the three years ended December 31, 2017 were as follows: Year Ended December 31, 2017 2016 2015 Income taxes paid $ 714 $ 15,271 $ 3,409

Liability for Unpaid Claims (Ta

Liability for Unpaid Claims (Tables)	12 Months Ended
	Dec. 31, 2017
Insurance [Abstract]
Summary of Liability for Unpaid Health Claims	Activity in the liability for unpaid health claims is summarized as follows: Year Ended December 31, 2017 2016 2015 Balance at beginning of year $ 143,128 $ 137,120 $ 128,265 Incurred related to: Current year 520,528 510,075 502,009 Prior years (8,048 ) (1,127 ) (7,845 ) Total incurred 512,480 508,948 494,164 Paid related to: Current year 394,506 386,278 379,037 Prior years 114,237 116,662 106,272 Total paid 508,743 502,940 485,309 Balance at end of year $ 146,865 $ 143,128 $ 137,120
Short-duration Insurance Contracts, Claims Development [Table Text Block]	The following table illustrates the total incurred claims for short-duration products over the last five years for the year ended December 31, 2017 . Claim frequency is determined by duration and incurred date. For the years ended December 31, 2017 As of December 31, 2017 Cumulative incurred claims (1) Total of incurred-but-not-reported liabilities plus expected development on reported claims Cumulative number of reported claims (1) (In thousands) Accident Year 2013 2014 2015 2016 2017 2013 $ 84,111 $ 82,644 $ 83,151 $ 83,119 $ 83,103 $ — 1,337 2014 101,407 99,876 99,810 99,777 — 1,600 2015 141,667 141,460 141,259 17 2,224 2016 140,944 138,899 431 2,158 2017 134,677 24,259 1,765 Total $ 597,715 $ 24,707 (1) The incurred claims and cumulative number of reported claims for all years prior to 2017 are unaudited. This table illustrates the total cumulative paid claims and allocated claims for short-duration products over the last five years for the year ended December 31, 2017 . Cumulative paid claims (1) For the years ended December 31, Accident Year 2013 2014 2015 2016 2017 2013 $ 68,159 $ 82,408 $ 83,131 $ 83,119 $ 83,103 2014 81,054 99,545 99,791 99,777 2015 115,922 140,982 141,242 2016 114,720 138,468 2017 110,418 Total 573,008 Short-duration claim liability as of December 31, 2017 24,707 Total incurred claims & IBNR $ 597,715 (1) The cumulative paid claims for all years prior to 2017 are unaudited.
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability	Below is the reconciliation of the net incurred and paid claims development tables to the liability for "Policy claims and other benefits payable" in the Consolidated Balance Sheets . December 31, 2017 December 31, 2016 Policy claims and other benefits payable: Short-duration products $ 24,707 $ 26,721 Insurance lines other than short duration—health 122,158 116,407 Total health 146,865 143,128 Insurance lines other than short duration—life 186,429 156,437 Total policy claims and other benefits payable $ 333,294 $ 299,565

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Components of Income Taxes	The components of income taxes were as follows: Year Ended December 31, 2017 2016 2015 Income tax expense (benefit) from continuing operations $ (627,615 ) $ 232,645 $ 249,894 Shareholders’ equity: Other comprehensive income (loss) 318,475 186,206 (411,646 ) Tax basis compensation expense (from the exercise of stock options and vesting of restricted stock awards) in excess of amounts recognized for financial reporting purposes — — (17,577 ) $ (309,140 ) $ 418,851 $ (179,329 )
Income Tax Expense from Continuing Operations	Income tax (benefit) expense from continuing operations consists of: Year Ended December 31, 2017 2016 2015 Current income tax (benefit) expense $ 138,262 $ 132,806 $ 174,284 Deferred income tax (benefit) expense (765,877 ) 99,839 75,610 $ (627,615 ) $ 232,645 $ 249,894
Summary of Effective Income Tax Rate	The effective income tax rate differed from the expected 35% rate as shown below: Year Ended December 31, 2017 % 2016 % 2015 % Expected income taxes $ 290,727 35.0 $ 270,282 35.0 $ 268,165 35.0 Increase (reduction) in income taxes resulting from: Tax reform adjustment (877,400 ) (105.6 ) — — — — Low income housing investments (18,515 ) (2.2 ) (18,202 ) (2.4 ) (19,031 ) (2.5 ) Share-based awards (19,549 ) (2.4 ) (18,653 ) (2.4 ) — — Other (2,878 ) (0.4 ) (782 ) (0.1 ) 760 0.1 Income tax expense (benefit) from continuing operations $ (627,615 ) (75.6 ) $ 232,645 30.1 $ 249,894 32.6
Significant Portions of Deferred Tax Assets and Deferred Tax Liabilities	The tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and deferred tax liabilities are presented below: December 31, 2017 2016 Deferred tax assets: Fixed maturity investments $ 8,692 $ 15,004 Carryover of tax losses 4,760 3,906 Total gross deferred tax assets 13,452 18,910 Deferred tax liabilities: Unrealized gains 380,251 315,509 Employee and agent compensation 65,576 92,131 Deferred acquisition costs 618,889 975,873 Future policy benefits, unearned and advance premiums, and policy claims 248,752 391,451 Other liabilities 11,289 3,987 Total gross deferred tax liabilities 1,324,757 1,778,951 Net deferred tax liability $ 1,311,305 $ 1,760,041

Postretirement Benefits (Tables

Postretirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total Cost of Retirement Plans Charged to Operations	The total cost of these retirement plans charged to operations was as follows: Year Ended December 31, Defined (1) Defined (2) 2017 $ 4,145 $ 28,828 2016 3,614 24,202 2015 3,429 29,230 (1) 401K plans (2) Qualified pension plans and SERPs
Schedule of Defined Benefit Plans Disclosures	The following table includes activity for the SERPs for the three years ended December 31, 2017 . Year Ended December 31, 2017 2016 2015 Premiums paid for insurance coverage $ 2,050 $ 2,050 $ 10,068 December 31, 2017 2016 Total investments: Company owned life insurance $ 40,273 $ 37,267 Exchange traded funds 55,442 48,999 $ 95,715 $ 86,266 Liability: Active plan $ 81,457 $ 74,687 Closed plan $ 3,008 $ 3,220
Pension Assets by Component at Fair Value	The following table presents the assets of Torchmark’s defined benefit pension plans for the years ended December 31, 2017 and 2016 . Pension Assets by Component at December 31, 2017 Fair Value Determined by: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Amount % to Total Corporate bonds: Financial $ $ 43,451 $ $ 43,451 12 Utilities 46,144 46,144 12 Energy 25,023 25,023 7 Other corporates 65,888 65,888 17 Total corporate bonds — 180,506 — 180,506 48 Exchange traded fund (1) 164,351 164,351 43 Other bonds 256 256 — Other long-term investments 2,304 2,304 1 Guaranteed annuity contract (2) 21,202 21,202 6 Short-term investments 3,984 3,984 1 Other 5,021 5,021 1 Grand Total $ 173,356 $ 204,268 $ — $ 377,624 100 (1) A fund including marketable securities that mirror the S&P 500 index. (2) Representing a guaranteed annuity contract issued by Torchmark's subsidiary, American Income Life Insurance Company, to fund the obligations of the American Income Pension Plan. Pension Assets by Component at December 31, 2016 Fair Value Determined by: Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Amount % to Total Corporate bonds: Financial $ $ 41,578 $ $ 41,578 13 Utilities 43,890 43,890 13 Energy 25,427 25,427 8 Other corporates 49,141 49,141 15 Total corporate bonds — 160,036 — 160,036 49 Exchange traded fund (1) 134,771 134,771 41 Other bonds 258 258 — Guaranteed annuity contract (2) 18,997 18,997 6 Short-term investments 7,391 7,391 2 Other 7,418 7,418 2 Grand Total $ 149,580 $ 179,291 $ — $ 328,871 100 (1) A fund including marketable securities that mirror the S&P 500 index. (2) Representing a guaranteed annuity contract issued by Torchmark's subsidiary, American Income Life Insurance Company, to fund the obligations of the American Income Pension Plan.
Analysis of Impact on Other Comprehensive Income (Loss)	An analysis of the impact on other comprehensive income (loss) concerning pensions and other postretirement benefits is as follows: Year Ended December 31, 2017 2016 2015 Balance at January 1 $ (173,883 ) $ (152,149 ) $ (152,999 ) Amortization of: Prior service cost 476 477 377 Net actuarial (gain) loss (1) 11,960 9,691 14,209 Total amortization 12,436 10,168 14,586 Plan amendments — — (2,104 ) Experience gain (loss) (31,933 ) (31,902 ) (11,632 ) Balance at December 31 $ (193,380 ) $ (173,883 ) $ (152,149 ) (1) Includes amortization of postretirement benefits other than pensions of $155 thousand in 2017 , $33 thousand in 2016 , and $120 thousand in 2015 .
Portion of Other Comprehensive Income Expected to Be Reflected in Pension Expense in Next Year	The portion of other comprehensive income that is expected to be reflected in pension expense in 2018 is as follows: Amortization of prior service cost $ 476 Amortization of net actuarial loss 14,543 Total $ 15,019
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted Average Assumptions	Weighted Average Pension Plan Assumptions For Benefit Obligations at December 31: 2017 2016 Discount Rate 3.75 % 4.27 % Rate of Compensation Increase 4.37 4.31 For Periodic Benefit Cost for the Year: 2017 2016 2015 Discount Rate 4.27 % 4.64 % 4.23 % Expected Long-Term Returns 6.96 7.19 6.96 Rate of Compensation Increase 4.31 4.33 4.35
Components of Net Periodic Pension Costs and Post-Retirement Benefit Costs	Net periodic pension cost for the defined benefit plans by expense component was as follows: Year Ended December 31, 2017 2016 2015 Service cost—benefits earned during the period $ 17,942 $ 15,502 $ 15,902 Interest cost on projected benefit obligation 22,124 21,631 19,887 Expected return on assets (23,597 ) (23,127 ) (21,204 ) Net amortization 12,281 10,135 14,465 Recognition of actuarial loss 78 61 180 Net periodic pension cost $ 28,828 $ 24,202 $ 29,230
Reconciliation of Benefit Obligation and Plan Assets	The following table presents a reconciliation from the beginning to the end of the year of the projected benefit obligation and plan assets for pensions. This table also presents the amounts previously recognized as a component of accumulated other comprehensive income. Pension Benefits Year Ended December 31, 2017 2016 Changes in benefit obligation: Obligation at beginning of year $ 527,522 $ 476,581 Service cost 17,942 15,502 Interest cost 22,124 21,631 Plan amendments — — Actuarial loss (gain) 55,369 34,667 Benefits paid (20,351 ) (20,859 ) Obligation at end of year 602,606 527,522 Changes in plan assets: Fair value at beginning of year 328,871 307,596 Return on assets 47,832 26,377 Contributions 21,272 15,757 Benefits paid (20,351 ) (20,859 ) Fair value at end of year 377,624 328,871 Funded status at year end $ (224,982 ) $ (198,651 )
Schedule of Amounts Recognized as Components Accumulated Other Comprehensive Income	Amounts recognized in accumulated other comprehensive income consist of: Net loss (gain) $ 186,563 $ 167,313 Prior service cost 4,135 4,611 Net amounts recognized at year end $ 190,698 $ 171,924
Estimated Future Payments for Post-Retirement Benefit Plans	Torchmark has estimated its expected pension benefits to be paid over the next ten years as of December 31, 2017 . These estimates use the same assumptions that measure the benefit obligation at December 31, 2016 , taking estimated future employee service into account. Those estimated benefits are as follows: For the year(s) 2018 $ 20,375 2019 22,143 2020 23,840 2021 25,239 2022 27,090 2023-2027 160,075
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted Average Assumptions	The table below presents the assumptions used to determine the liabilities and costs of Torchmark’s postretirement benefit plans other than pensions. Weighted Average Assumptions for Postretirement Benefit Plans Other Than Pensions For Benefit Obligations at December 31: 2017 2016 Discount Rate 3.76 % 4.29 % For Periodic Benefit Cost for the Year: 2017 2016 2015 Discount Rate 4.29 % 4.66 % 4.23 %
Components of Net Periodic Pension Costs and Post-Retirement Benefit Costs	The components of net periodic postretirement benefit cost for plans other than pensions are as follows: Year Ended December 31, 2017 2016 2015 Service cost $ — $ — $ — Interest cost on benefit obligation 1,132 1,139 1,075 Expected return on plan assets — — — Net amortization 155 33 120 Recognition of net actuarial (gain) loss 167 (132 ) 367 Net periodic postretirement benefit cost $ 1,454 $ 1,040 $ 1,562
Reconciliation of Benefit Obligation and Plan Assets	The following table presents a reconciliation of the benefit obligation and plan assets from the beginning to the end of the year. As these plans are unfunded, funded status is equivalent to the accrued benefit liability. Benefits Other Than Pensions Year Ended December 31, 2017 2016 Changes in benefit obligation: Obligation at beginning of year $ 23,721 $ 22,479 Service cost — — Interest cost 1,132 1,139 Actuarial loss (gain) 1,045 412 Benefits paid (285 ) (309 ) Obligation at end of year 25,613 23,721 Changes in plan assets: Fair value at beginning of year — — Return on assets — — Contributions 285 309 Benefits paid (285 ) (309 ) Fair value at end of year — — Funded status at year end $ (25,613 ) $ (23,721 )
Schedule of Amounts Recognized as Components Accumulated Other Comprehensive Income	Amounts recognized in accumulated other comprehensive income: Net loss (1) $ 2,682 $ 1,959 Net amounts recognized at year end $ 2,682 $ 1,959 (1) The net loss for benefit plans other than pensions reduces other comprehensive income.
Estimated Future Payments for Post-Retirement Benefit Plans	Estimated Future Payments for Post-Retirement Benefit Plans Other Than Pensions For the year(s) 2018 $ 1,228 2019 1,278 2020 1,311 2021 1,344 2022 1,386 2023-2027 7,515

Supplemental Disclosures of C37

Supplemental Disclosures of Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Summary of Noncash Transactions	The following table summarizes Torchmark’s noncash transactions, which are not reflected on the Consolidated Statements of Cash Flows: Year Ended December 31, 2017 2016 2015 Stock-based compensation not involving cash $ 37,034 $ 26,326 $ 28,664 Commitments for low-income housing interests 33,846 56,818 68,949 Exchanges of fixed maturity investments 84,312 224,901 — Net unsettled security trades — 15,020 —
Summary of Amounts Paid	The following table summarizes certain amounts paid during the period: Year Ended December 31, 2017 2016 2015 Interest paid $ 82,494 $ 81,338 $ 74,792 Income taxes paid 74,379 79,790 110,650

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Selected Information about Debt Issues	The following table presents information about the terms and outstanding balances of Torchmark’s debt. Selected Information about Debt Issues As of December 31, 2017 2016 Annual Interest Rate Issue Date Periodic Interest Payments Due Outstanding Principal (Par Value) Outstanding Principal (Book Value) Outstanding Principal (Fair Value) Outstanding Principal (Book Value) Long-term debt: Notes, due 5/15/23 (3,5) 7.875 % 5/93 5/15 & 11/15 $ 165,612 $ 164,284 $ 195,786 $ 164,095 Senior Notes, due 6/15/19 (3,7) 9.250 % 6/09 6/15 & 12/15 292,647 291,888 320,697 291,424 Senior Notes, due 9/15/22 (3,7) 3.800 % 9/12 3/15 & 9/15 150,000 148,477 155,000 148,189 Junior Subordinated Debentures due 12/15/52 (4,8,12) 5.875 % 9/12 quarterly — — — 120,929 Junior Subordinated Debentures due 3/15/36 (4,6,12) 4.888 % (13) (11) quarterly 20,000 20,000 20,000 20,000 Junior Subordinated Debentures due 6/15/56 (4,9) 6.125 % 4/16 quarterly 300,000 290,460 321,120 290,403 Junior Subordinated Debentures due 11/17/57 (4,10) 5.275 % 11/17 6/15 & 12/15 125,000 123,342 122,039 — Term loan due 5/17/21 (1,6) 2.600 % (14) 6/16 monthly 98,125 98,125 98,125 100,000 1,151,384 1,136,576 1,232,767 1,135,040 Less current maturity of term loan 4,375 4,375 4,375 1,875 Total long-term debt 1,147,009 1,132,201 1,228,392 1,133,165 Short-term debt: Current maturity of term loan 4,375 4,375 4,375 1,875 Commercial paper (2) 324,250 323,692 323,692 262,600 Total short-term debt 328,625 328,067 328,067 264,475 Total debt $ 1,475,634 $ 1,460,268 $ 1,556,459 $ 1,397,640 (1) The term loan has higher priority than all other debt issues. (2) Commercial paper has priority over all other debt except the term loan. (3) All securities, other than the term loan, commercial paper and Junior Subordinated Debentures have equal priority with one another. (4) All Junior Subordinated Debentures have equal priority, but are subordinate to all other issues. (5) Not callable. (6) Callable anytime. (7) Callable subject to “make-whole” premium. (8) Redeemed on December 22, 2017. (9) Callable at any time on or after June15, 2021, and prior to this date upon the occurrence of a Tax Event or Rating Agency Event. (10) Callable at any time on or after November 17, 2022, and prior to this date upon the occurrence of a Tax Event or Rating Agency Event. (11) Assumed upon November 1, 2012 acquisition of Family Heritage. (12) Quarterly payments on the 15th of March, June, September, and December. (13) Interest paid at 3 Month LIBOR plus 330 basis points, resets each quarter. (14) Interest paid at 1 Month LIBOR plus 125 basis points, resets each month.
Schedule of Maturities of Long-term Debt	The following table presents expected scheduled principal payments under our contractual debt obligations: Year Ended December 31, 2018 2019 2020 2021 2022 Thereafter Debt obligations $ 328,625 $ 299,522 $ 9,375 $ 77,500 $ 150,000 $ 610,612
Short-Term Borrowings	Credit Facility - Commercial Paper At December 31, 2017 2016 Balance at end of period (at par value) $ 324,250 $ 262,850 Annualized interest rate 1.78 % 0.96 % Letters of credit outstanding $ 177,000 $ 177,000 Remaining amount available under credit line 248,750 310,150 Year Ended December 31, 2017 2016 2015 Average balance outstanding during period $ 323,429 $ 301,550 $ 350,851 Daily-weighted average interest rate (annualized) 1.30 % 0.83 % 0.43 % Maximum daily amount outstanding during period $ 455,912 $ 412,676 $ 458,110

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Summary of Preferred and Common Share Activity	A summary of preferred and common share activity is presented in the following chart. Preferred Stock Common Stock Issued Treasury Stock Issued Treasury Stock 2015: Balance at January 1, 2015 — — 134,218,183 (6,287,907 ) Grants of restricted stock 6,648 Forfeitures of restricted stock (13,950 ) Vesting of performance shares 211,287 Issuance of common stock due to exercise of stock options 1,576,485 Treasury stock acquired (7,340,794 ) Retirement of treasury stock (4,000,000 ) 4,000,000 Balance at December 31, 2015 — — 130,218,183 (7,848,231 ) 2016: Grants of restricted stock 12,549 Forfeitures of restricted stock — Vesting of performance shares 159,020 Issuance of common stock due to exercise of stock options 2,184,169 Treasury stock acquired (6,694,582 ) Retirement of treasury stock (3,000,000 ) 3,000,000 Balance at December 31, 2016 — — 127,218,183 (9,187,075 ) 2017: Grants of restricted stock 9,135 Vesting of performance shares 119,896 Issuance of common stock due to exercise of stock options 1,661,808 Treasury stock acquired (5,228,868 ) Retirement of treasury stock (3,000,000 ) 3,000,000 Balance at December 31, 2017 — — 124,218,183 (9,625,104 )
Reconciliation of Basic and Diluted Weighted Average Shares Outstanding	A reconciliation of basic and diluted weighted-average shares outstanding used in the computation of basic and diluted earnings per share is as follows: Year Ended December 31, 2017 2016 2015 Basic weighted average shares outstanding 116,342,529 120,001,191 125,094,628 Weighted average dilutive options outstanding 2,640,965 2,366,594 1,662,607 Diluted weighted average shares outstanding 118,983,494 122,367,785 126,757,235

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Grant Contract Periods and Vesting Periods	Options generally vest in accordance with the following schedule: Shares vested by period Contract Period 6 Months Year 1 Year 2 Year 3 Year 4 Year 5 Directors 7 years 100% Employees 7 years —% —% 50% 50% Employees (1) 10 years —% —% 25% 25% 25% 25% (1) Grant offered through the Torchmark Corporation 2011 Incentive Plan only.
Analysis of Shares Available for Grant	An analysis of shares available for grant is as follows: Available for Grant 2017 2016 2015 Balance at January 1, 5,088,461 6,872,282 8,458,593 Options expired and forfeited during year (1) 26,488 8,518 90,371 Restricted stock expired and forfeited during year (2) 46,500 — 89,745 Options granted during year (1) (1,328,513 ) (1,306,306 ) (1,334,514 ) Restricted stock, restricted stock units, and performance shares granted under the Torchmark Corporation 2011 Incentive Plan (2) (868,616 ) (486,033 ) (431,913 ) Balance at December 31, 2,964,320 5,088,461 6,872,282 (1) Plan allows for grant of options such that each grant reduces shares available for grant in a range from 0.85 share to 1 share. (2) Plan allows for grant of restricted stock such that each stock grant reduces shares available for grant in a range from 3.1 shares to 3.88 shares.
Summary of Stock Compensation Activity	Selected stock option activity for the three years ended December 31, 2017 is presented below: 2017 2016 2015 Weighted-average grant-date fair value of options granted $ 12.88 $ 9.04 $ 11.97 Intrinsic value of options exercised 70,948 73,995 54,854 Cash received from options exercised 61,215 61,329 35,958 Actual tax benefit received 24,832 25,898 24,470 A summary of stock compensation activity for each of the three years ended December 31, 2017 is presented below: 2017 2016 2015 Stock-based compensation expense recognized (1) $ 37,034 $ 26,326 $ 28,664 Tax benefit recognized 32,511 27,867 10,033 (1) No stock-based compensation expense was capitalized in any period.
Schedule of Additional Information of Stock-Based Compensation	Additional information about Torchmark’s stock option activity as of December 31, 2017 and 2016 is as follows: 2017 2016 Outstanding options: Weighted-average remaining contractual term (in years) 4.89 4.70 Aggregate intrinsic value $ 231,277 $ 87,286 Exercisable options: Weighted-average remaining contractual term (in years) 2.99 2.96 Aggregate intrinsic value $ 137,424 $ 63,395 Additional stock compensation information is as follows at December 31: 2017 2016 Unrecognized compensation (1) $ 31,309 $ 27,334 Weighted average period of expected recognition (in years) (1) 0.86 0.89 (1) Includes restricted stock and performance shares.
Summary of Options Outstanding	The following table summarizes information about stock options outstanding at December 31, 2017 . Options Outstanding Options Exercisable Range of Number Outstanding Weighted- Average Remaining Contractual Life (Years) Weighted- Average Exercise Price Number Exercisable Weighted- Average Exercise Price $29.59 - $37.40 1,421,268 2.20 $ 34.54 1,366,689 $ 34.42 50.64 1,405,725 6.39 50.64 — — 50.69 - 51.62 1,090,703 3.69 50.70 958,463 50.70 53.61 - 56.32 1,384,582 4.63 53.65 594,184 53.71 73.92 - 77.26 1,451,523 7.23 77.24 9,643 73.92 $29.59 - $77.26 6,753,801 4.89 $ 53.59 2,928,979 $ 43.79
Analysis of Option Activity	An analysis of option activity for each of the three years ended December 31, 2017 is as follows: 2017 2016 2015 Options Weighted Average Exercise Price Options Weighted Average Exercise Price Options Weighted Average Exercise Price Outstanding—beginning of year 6,973,591 $ 44.64 7,734,841 $ 38.84 7,889,321 $ 32.91 Granted: 7-year term 933,286 77.19 834,212 50.78 1,220,751 53.62 10-year term 535,220 77.26 597,225 50.64 296,875 53.61 Exercised (1,661,808 ) 36.84 (2,184,169 ) 28.08 (1,576,485 ) 22.81 Expired and forfeited (26,488 ) 57.94 (8,518 ) 39.35 (95,621 ) 48.85 Outstanding—end of year 6,753,801 $ 53.59 6,973,591 $ 44.64 7,734,841 $ 38.84 Exercisable at end of year 2,928,979 $ 43.79 3,115,847 $ 36.81 3,774,061 $ 29.37
Schedule of Additional Information on Unvested Options	Additional information concerning Torchmark’s unvested options is as follows at December 31: 2017 2016 Number of shares outstanding 3,824,822 3,857,744 Weighted-average exercise price (per share) $ 61.10 $ 50.97 Weighted-average remaining contractual term (in years) 6.34 6.11 Aggregate intrinsic value $ 113,246 $ 23,891
Schedule of Performance Shares Settled	Below is the final determination of the performance share grants in 2013 to 2015: Year of grants Final settlement of shares Final settlement date 2013 159,020 February 24, 2016 2014 119,896 February 21, 2017 2015 149,898 February 27, 2018
Summary of Restricted Stock and Restricted Stock Units Granted	A summary of restricted stock grants for each of the years in the three-year period ended December 31, 2017 is presented in the table below. 2017 2016 2015 Directors restricted stock: Shares 9,135 12,549 6,648 Price per share $ 73.92 $ 57.39 $ 54.16 Aggregate value $ 675 $ 720 $ 360 Percent vested as of 12/31/17 100 % 85 % 100 % Directors restricted stock units (including dividend equivalents): Shares 7,735 6,912 7,640 Price per share $ 74.45 $ 56.74 $ 54.44 Aggregate value $ 576 $ 392 $ 416 Percent vested as of 12/31/17 100 % 100 % 100 % Performance shares: Target shares 153,000 167,500 179,500 Target price per share $ 77.26 $ 50.64 $ 53.61 Assumed adjustment for performance objectives (in shares) 106,084 (35,073 ) (58,056 ) Aggregate value $ 11,821 $ 8,482 $ 9,623 Percent vested as of 12/31/17 — % — % — %
Analysis of Unvested Restricted Stock	An analysis of unvested restricted stock is as follows: Executive Executive Directors Directors Total 2015: Balance at January 1, 2015 263,430 556,360 — — 819,790 Grants — 179,500 6,648 7,640 193,788 Additional performance shares (1) (58,056 ) (58,056 ) Restriction lapses (61,815 ) (211,287 ) (6,648 ) (7,640 ) (287,390 ) Forfeitures (13,950 ) (7,500 ) (21,450 ) Balance at December 31, 2015 187,665 459,017 — — 646,682 2016: Grants — 167,500 12,549 6,912 186,961 Additional performance shares (1) (35,073 ) (35,073 ) Restriction lapses (130,215 ) (159,020 ) (10,655 ) (6,912 ) (306,802 ) Forfeitures — — — Balance at December 31, 2016 57,450 432,424 1,894 — 491,768 2017: Grants — 153,000 9,135 7,735 169,870 Additional performance shares (1) 106,084 106,084 Restriction lapses (14,700 ) (119,896 ) (11,029 ) (7,735 ) (153,360 ) Forfeitures (7,500 ) (7,500 ) (15,000 ) Balance at December 31, 2017 35,250 564,112 — — 599,362 (1) Estimated additional (reduced) share grants expected due to achievement of performance criteria.
Schedule of Weighted-Average Grant-Date Fair Values of Unvested Restricted Stock	An analysis of the weighted-average grant-date fair values per share of unvested restricted stock is as follows for the year 2017 : Executive Restricted Stock Executive Performance Shares Directors Restricted Stock Directors Restricted Stock Units Grant-date fair value per share at January 1, 2017 $ 38.46 $ 49.79 $ 63.39 Grants — 77.26 73.92 $ 73.92 Estimated additional performance shares 71.76 Restriction lapses (30.69 ) (72.42 ) (72.11 ) (73.92 ) Forfeitures (37.40 ) (43.85 ) Grant-date fair value per share at December 31, 2017 41.93 56.64

Business Segments (Tables)

Business Segments (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Schedule of Segment Premium Revenue by Each Marketing Group	The tables below present segment premium revenue by each of Torchmark’s distribution channels. Torchmark Corporation Premium Income by Distribution Channel For the Year 2017 Life Health Annuity Total Distribution Channel Amount % of Total Amount % of Total Amount % of Total Amount % of Total United American Independent $ 12,547 1 $ 364,128 37 $ 15 100 $ 376,690 12 Liberty National Exclusive 274,635 12 196,207 20 470,842 14 American Income Exclusive 999,279 43 89,036 9 1,088,315 33 Family Heritage Exclusive 3,193 — 253,534 26 256,727 8 Direct Response 812,907 35 73,468 8 886,375 27 Other 203,986 9 203,986 6 $ 2,306,547 100 $ 976,373 100 $ 15 100 $ 3,282,935 100 For the Year 2016 Life Health Annuity Total Distribution Channel Amount % of Total Amount % of Total Amount % of Total Amount % of Total United American Independent $ 13,733 1 $ 355,015 38 $ 38 100 $ 368,786 12 Liberty National Exclusive 270,476 12 201,798 21 472,274 15 American Income Exclusive 913,355 42 84,382 9 997,737 32 Family Heritage Exclusive 2,866 — 236,075 25 238,941 8 Direct Response 782,765 36 70,393 7 853,158 27 Other 206,138 9 206,138 6 $ 2,189,333 100 $ 947,663 100 $ 38 100 $ 3,137,034 100 For the Year 2015 Life Health Annuity Total Distribution Channel Amount % of Total Amount % of Total Amount % of Total Amount % of Total United American Independent $ 15,036 1 $ 345,330 37 $ 135 100 $ 360,501 12 Liberty National Exclusive 271,113 13 209,150 23 480,263 16 American Income Exclusive 830,903 40 80,339 9 911,242 30 Family Heritage Exclusive 2,334 — 221,091 24 223,425 8 Direct Response 746,693 36 69,610 7 816,303 27 Other 206,986 10 206,986 7 $ 2,073,065 100 $ 925,520 100 $ 135 100 $ 2,998,720 100
Reconciliation of Segment Operating Information to Consolidated Statement of Operations	The following tables set forth a reconciliation of Torchmark’s revenues and operations by segment to its major income statement line items. See Note 1—Significant Accounting Policies for additional information concerning reconciling items of segment profits to pretax income. For the year 2017 Life Health Annuity Investment Corporate & Other Adjustments Consolidated Revenue: Premium $ 2,306,547 $ 976,373 $ 15 $ 3,282,935 Net investment income $ 847,885 847,885 Other income $ 1,270 $ (128 ) (2) 1,142 Total revenue 2,306,547 976,373 15 847,885 1,270 (128 ) 4,131,962 Expenses: Policy benefits 1,549,602 628,640 35,836 13,797 (3,4) 2,227,875 Required interest on: Policy reserves (607,007 ) (77,792 ) (49,571 ) 734,370 — Deferred acquisition costs 186,236 23,454 690 (210,380 ) — Amortization of acquisition costs 396,268 96,519 2,466 (4,850 ) (4) 490,403 Commissions, premium taxes, and non-deferred acquisition costs 177,111 86,044 32 1,673 (2,5) 264,860 Insurance administrative expense (1) 210,590 210,590 Parent expense 9,631 9,631 Stock-based compensation expense 33,654 3,380 (6) 37,034 Interest expense 84,532 84,532 Total expenses 1,702,210 756,865 (10,547 ) 608,522 253,875 14,000 3,324,925 Subtotal 604,337 219,508 10,562 239,363 (252,605 ) (14,128 ) 807,037 Non-operating items 14,128 (3,4,5,6) 14,128 Measure of segment profitability (pretax) $ 604,337 $ 219,508 $ 10,562 $ 239,363 $ (252,605 ) $ — 821,165 Deduct applicable income taxes (247,484 ) Net operating income from continuing operations 573,681 Add back income taxes applicable to segment profitability 247,484 Add (deduct) realized investment gains (losses) 23,611 Deduct administrative settlements (8,659 ) Deduct non-operating expenses (288 ) Deduct guaranty fund assessments (1,801 ) Deduct increase in stock-based compensation expense due to Tax Legislation (3,380 ) Income before income taxes per Consolidated Statement of Operations $ 830,648 (1) Administrative expense is not allocated to insurance segments. (2) Elimination of intersegment commission. (3) Administrative settlements. (4) Non-operating expense. (5) Guaranty fund assessments. (6) Recognition of a one-time increase in stock-based compensation expense due to Tax Legislation. For the year 2016 Life Health Annuity Investment Corporate & Other Adjustments Consolidated Revenue: Premium $ 2,189,333 $ 947,663 $ 38 $ 3,137,034 Net investment income $ 806,903 806,903 Other income $ 1,534 $ (159 ) (2) 1,375 Total revenue 2,189,333 947,663 38 806,903 1,534 (159 ) 3,945,312 Expenses: Policy benefits 1,475,477 612,725 36,751 3,795 (3) 2,128,748 Required interest on: Policy reserves (577,827 ) (73,382 ) (51,131 ) 702,340 — Deferred acquisition costs 178,946 23,060 807 (202,813 ) — Amortization of acquisition costs 374,499 90,385 4,179 469,063 Commissions, premium taxes, and non-deferred acquisition costs 164,476 84,819 38 (159 ) (2) 249,174 Insurance administrative expense (1) 196,598 553 (4) 197,151 Parent expense 8,587 8,587 Stock-based compensation expense 26,326 26,326 Interest expense 83,345 83,345 Total expenses 1,615,571 737,607 (9,356 ) 582,872 231,511 4,189 3,162,394 Subtotal 573,762 210,056 9,394 224,031 (229,977 ) (4,348 ) 782,918 Non-operating items 4,348 (3,4) 4,348 Measure of segment profitability (pretax) $ 573,762 $ 210,056 $ 9,394 $ 224,031 $ (229,977 ) $ — 787,266 Deduct applicable income taxes (237,906 ) Net operating income from continuing operations 549,360 Add back income taxes applicable to segment profitability 237,906 Add (deduct) realized investment gains (losses) (10,683 ) Deduct administrative settlements (3,795 ) Deduct non-operating fees (553 ) Income before income taxes per Consolidated Statement of Operations $ 772,235 (1) Administrative expense is not allocated to insurance segments. (2) Elimination of intersegment commission. (3) Administrative settlements. (4) Non-operating fees. For the Year 2015 Life Health Annuity Investment Corporate & Other Adjustments Consolidated Revenue: Premium $ 2,073,065 $ 925,520 $ 135 $ 2,998,720 Net investment income $ 773,951 773,951 Other income $ 2,379 $ (194 ) (2) 2,185 Total revenue 2,073,065 925,520 135 773,951 2,379 (194 ) 3,774,856 Expenses: Policy benefits 1,374,608 602,610 38,994 2,016,212 Required interest on: Policy reserves (552,298 ) (69,057 ) (53,295 ) 674,650 — Deferred acquisition costs 172,947 22,760 1,138 (196,845 ) — Amortization of acquisition costs 353,595 83,341 8,689 445,625 Commissions, premium taxes, and non-deferred acquisition costs 154,811 81,489 41 1,200 (2,3) 237,541 Insurance administrative expense (1) 186,191 186,191 Parent expense 9,003 9,003 Stock-based compensation expense 28,664 28,664 Interest expense 76,642 76,642 Total expenses 1,503,663 721,143 (4,433 ) 554,447 223,858 1,200 2,999,878 Subtotal 569,402 204,377 4,568 219,504 (221,479 ) (1,394 ) 774,978 Non-operating items 1,394 (3) 1,394 Measure of segment profitability (pretax) $ 569,402 $ 204,377 $ 4,568 $ 219,504 $ (221,479 ) $ — 776,372 Deduct applicable income taxes (253,459 ) Net operating income from continuing operations 522,913 Add back income taxes applicable to segment profitability 253,459 Add (deduct) realized investment gains (losses) (8,791 ) Deduct administrative settlements (1,394 ) Income before income taxes per Consolidated Statement of Operations $ 766,187 (1) Administrative expense is not allocated to insurance segments. (2) Elimination of intersegment commission. (3) Administrative settlements.
Assets by Segment	The table below reconciles segment assets to total assets as reported in the consolidated financial statements. Assets by Segment At December 31, 2017 Life Health Annuity Investment Other Consolidated Cash and invested assets $ 17,853,047 $ 17,853,047 Accrued investment income 233,453 233,453 Deferred acquisition costs $ 3,423,296 $ 529,068 $ 5,699 3,958,063 Goodwill 309,609 131,982 441,591 Other assets $ 988,831 988,831 Total assets $ 3,732,905 $ 661,050 $ 5,699 $ 18,086,500 $ 988,831 $ 23,474,985 At December 31, 2016 Life Health Annuity Investment Other Consolidated Cash and invested assets $ 15,955,891 $ 15,955,891 Accrued investment income 223,148 223,148 Deferred acquisition costs $ 3,261,220 $ 512,701 $ 9,237 3,783,158 Goodwill 309,609 131,982 441,591 Other assets $ 1,032,299 1,032,299 Total assets $ 3,570,829 $ 644,683 $ 9,237 $ 16,179,039 $ 1,032,299 $ 21,436,087
Other Balances by Segment	Liabilities by Segment At December 31, 2017 Life Health Annuity Investment Other Consolidated Future policy benefits $ 10,353,286 $ 1,831,338 $ 1,254,848 $ 13,439,472 Unearned and advance premiums 16,927 44,503 61,430 Policy claims and other benefits payable 186,429 146,865 333,294 Debt $ 1,460,268 1,460,268 Other $ 1,949,100 1,949,100 Total liabilities $ 10,556,642 $ 2,022,706 $ 1,254,848 $ 1,460,268 $ 1,949,100 $ 17,243,564 At December 31, 2016 Life Health Annuity Investment Other Consolidated Future policy benefits $ 9,825,776 $ 1,706,870 $ 1,293,191 $ 12,825,837 Unearned and advance premiums 16,828 47,189 64,017 Policy claims and other benefits payable 156,437 143,128 299,565 Debt $ 1,397,640 1,397,640 Other $ 2,282,167 2,282,167 Total liabilities $ 9,999,041 $ 1,897,187 $ 1,293,191 $ 1,397,640 $ 2,282,167 $ 16,869,226

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Operating Leases of Lessee Disclosure	Rental expense for operating leases for each of the three years ended December 31, 2017 is as follows: Year Ended December 31, 2017 2016 2015 Rental expense $ 6,446 $ 6,520 $ 6,722 Future minimum rental commitments required under operating leases having remaining noncancelable lease terms in excess of one year at December 31, 2017 were as follows: Year Ended December 31, 2018 2019 2020 2021 2022 Thereafter Operating lease commitments $ 3,483 $ 3,298 $ 3,124 $ 2,886 $ 1,943 $ 1,830
Long-term Purchase Commitment	Year Ended December 31, 2018 2019 2020 2021 2022 Thereafter Purchase commitments $ 27,326 $ 9,198 $ 3,257 $ 2,213 $ 2,169 $ 246,836

Selected Quarterly Data (Unau43

Selected Quarterly Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Selected Quarterly Data	The following is an unaudited summary of quarterly results for the two years ended December 31, 2017 . The information includes all adjustments (consisting of normal accruals) which management considers necessary for a fair presentation of the results of operations for these periods. Three Months Ended March 31, June 30, September 30, December 31, 2017: Premium income $ 820,631 $ 816,614 $ 819,217 $ 826,473 Net investment income 208,282 212,776 213,872 212,955 Realized investment gains (losses) (5,748 ) (705 ) 12,595 17,469 Total revenue 1,023,581 1,029,078 1,046,015 1,056,899 Policyholder benefits 557,776 556,415 551,219 562,465 Amortization of deferred acquisition costs 125,908 122,121 122,334 120,040 Pretax income from continuing operations 191,741 201,926 220,610 216,371 Income from continuing operations 137,178 140,363 153,346 1,027,376 Income from discontinued operations (3,637 ) (90 ) (12 ) (30 ) Net income 133,541 140,273 153,334 1,027,346 Basic net income per common share: Continuing operations 1.16 1.20 1.32 8.93 Discontinued operations (0.03 ) — — — Total basic net income per common share 1.13 1.20 1.32 8.93 Diluted net income per common share: Continuing operations 1.14 1.18 1.29 8.71 Discontinued operations (0.03 ) — — — Total diluted net income per common share 1.11 1.18 1.29 8.71 Three Months Ended March 31, June 30, September 30, December 31, 2016: Premium income $ 779,860 $ 785,855 $ 783,411 $ 787,908 Net investment income 197,053 201,642 202,720 205,488 Realized investment gains (losses) 293 4,005 3,482 (18,463 ) Total revenue 977,627 991,884 989,773 975,345 Policyholder benefits 524,973 531,485 532,152 540,138 Amortization of deferred acquisition costs 118,806 117,245 116,821 116,191 Pretax income from continuing operations 195,448 199,344 201,461 175,982 Income from continuing operations 133,574 139,294 141,910 124,812 Income from discontinued operations (9,541 ) (865 ) 9,959 10,636 Net income 124,033 138,429 151,869 135,448 Basic net income per common share: Continuing operations 1.10 1.16 1.19 1.05 Discontinued operations (0.08 ) (0.01 ) 0.08 0.09 Total basic net income per common share 1.02 1.15 1.27 1.14 Diluted net income per common share: Continuing operations 1.08 1.13 1.16 1.03 Discontinued operations (0.07 ) — 0.09 0.09 Total diluted net income per common share 1.01 1.13 1.25 1.12

Significant Accounting Polici44

Significant Accounting Policies - Additional Information (Detail) $ in Thousands		Dec. 22, 2017USD ($)	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2018USD ($)	Jan. 01, 2018USD ($)
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%
Advanced agent commissions receivable			$ 378,000	$ 353,000
Advertising costs charged to earnings and included in other operating expense			9,300	9,300	$ 9,700
Capitalized advertising costs			1,280,000	1,250,000
Carrying value of investment in low-income housing interests			228,000	280,000
Obligations under future commitments for low-income housing interests			34,000
Original cost of property and equipment			217,000	196,000
Accumulated depreciation			109,000	99,000
Depreciation expense			$ 10,500	9,800	8,000
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			5.80%
Tax benefit as the result of a lower corporate tax rate			$ 877,000
Insurance policy charges			$ 17,000	18,300	$ 19,300
Term over which monthly data points are used to derive volatility			3 years
Reclassification from AOCI to retained earnings		$ 252,000
Retained earnings			$ 4,806,208	$ 3,890,798
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			10 years
Maximum | Equipment
Significant Accounting Policies [Line Items]
Property and equipment, estimated useful life			5 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			87.00%
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
Accounting Standards Update 2018-02
Significant Accounting Policies [Line Items]
Reclassification from AOCI to retained earnings	[1]		$ 252,000
Forecast | Accounting Standards Update 2017-07 | Minimum
Significant Accounting Policies [Line Items]
Impact of ASU on financial statements						$ 3,000
Forecast | Accounting Standards Update 2017-07 | Maximum
Significant Accounting Policies [Line Items]
Impact of ASU on financial statements						$ 5,000
Subsequent Event | Accounting Standards Update 2016-01
Significant Accounting Policies [Line Items]
Retained earnings							$ 6,000
[1]	Income tax effects of certain items were reclassified from accumulated other comprehensive income to retained earnings to remove stranded tax effects as a result of early adoption of ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. See further discussion in Note 1—Significant Accounting Policies.

Significant Accounting Polici45

Significant Accounting Policies - Summary of Assumptions for Options Granted (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Volatility factor	14.80%	19.20%	23.60%
Dividend yield	0.70%	1.10%	0.90%
Expected term (in years)	5 years 8 months 16 days	5 years 9 months 11 days	5 years 7 months 28 days
Risk-free rate	2.00%	1.30%	1.60%

Statutory Accounting - Consolid

Statutory Accounting - Consolidated Net Income and Shareholders' Equity for Insurance Companies (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Insurance [Abstract]
Life insurance subsidiaries, Net income	$ 426,285	$ 429,563	$ 393,466
Life insurance subsidiaries, Shareholders' equity	$ 1,254,875	$ 1,335,070

Statutory Accounting - Addition

Statutory Accounting - Additional Information (Detail) $ in Millions	Dec. 31, 2017USD ($)
Insurance [Abstract]
Surplus adequate to satisfy regulatory compliance	$ 458

Supplemental Information abou48

Supplemental Information about Changes to Accumulated Other Comprehensive Income - Schedule of Change in Balance by Component of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands		Dec. 22, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in AOCI, Net of Tax
Beginning balance			$ 4,566,861	$ 4,055,552	$ 4,697,466
Reclassifications, net of tax			(14,668)	10,574	11,517
Reclassification, Tax Reform		$ 252,000
Ending balance			6,231,421	4,566,861	4,055,552
Total [Member]
Increase (Decrease) in AOCI, Net of Tax
Beginning balance			577,574	231,947	997,452
Other comprehensive income (loss) before reclassifications, net of tax			608,968	335,053	(777,022)
Reclassifications, net of tax			(14,668)	10,574	11,517
Other comprehensive income (loss)			594,300	345,627	(765,505)
Reclassification, Tax Reform	[1]		252,400
Ending balance			1,424,274	577,574	231,947
Available for Sale Assets
Increase (Decrease) in AOCI, Net of Tax
Beginning balance			692,314	332,333	1,090,273
Other comprehensive income (loss) before reclassifications, net of tax			621,619	356,016	(759,976)
Reclassifications, net of tax			(22,751)	3,965	2,036
Other comprehensive income (loss)			598,868	359,981	(757,940)
Reclassification, Tax Reform			278,107
Ending balance			1,569,289	692,314	332,333
Deferred Acquisition Costs
Increase (Decrease) in AOCI, Net of Tax
Beginning balance			(6,682)	(5,115)	(10,758)
Other comprehensive income (loss) before reclassifications, net of tax			(350)	(1,567)	5,643
Reclassifications, net of tax			0	0	0
Other comprehensive income (loss)			(350)	(1,567)	5,643
Reclassification, Tax Reform			(1,515)
Ending balance			(8,547)	(6,682)	(5,115)
Foreign Exchange
Increase (Decrease) in AOCI, Net of Tax
Beginning balance			4,967	3,627	17,386
Other comprehensive income (loss) before reclassifications, net of tax			8,452	1,340	(13,759)
Reclassifications, net of tax			0	0	0
Other comprehensive income (loss)			8,452	1,340	(13,759)
Reclassification, Tax Reform			2,883
Ending balance			16,302	4,967	3,627
Pension Adjustments
Increase (Decrease) in AOCI, Net of Tax
Beginning balance			(113,025)	(98,898)	(99,449)
Other comprehensive income (loss) before reclassifications, net of tax			(20,753)	(20,736)	(8,930)
Reclassifications, net of tax			8,083	6,609	9,481
Other comprehensive income (loss)			(12,670)	(14,127)	551
Reclassification, Tax Reform			(27,075)
Ending balance			$ (152,770)	$ (113,025)	$ (98,898)
[1]	Income tax effects of certain items were reclassified from accumulated other comprehensive income to retained earnings to remove stranded tax effects as a result of early adoption of ASU 2018-02, Income Statement—Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. See further discussion in Note 1—Significant Accounting Policies.

Supplemental Information abou49

Supplemental Information about Changes to Accumulated Other Comprehensive Income - Summary of Reclassification out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unrealized gains (losses) on available for sale assets:
Realized (gains) losses									$ (23,611)	$ 10,683	$ 8,791
Amortization of (discount) premium	$ (212,955)	$ (213,872)	$ (212,776)	$ (208,282)	$ (205,488)	$ (202,720)	$ (201,642)	$ (197,053)	(847,885)	(806,903)	(773,951)
Income before income taxes	(216,371)	(220,610)	(201,926)	(191,741)	(175,982)	(201,461)	(199,344)	(195,448)	(830,648)	(772,235)	(766,187)
Income tax expense from continuing operations									(627,615)	232,645	249,894
Net income	$ (1,027,346)	$ (153,334)	$ (140,273)	$ (133,541)	$ (135,448)	$ (151,869)	$ (138,429)	$ (124,033)	(1,454,494)	(549,779)	(527,100)
Pension adjustments:
Total reclassifications (after tax)									(14,668)	10,574	11,517
Unrealized Gains (Losses) on Available for Sale Assets
Pension adjustments:
Total reclassifications (after tax)									(22,751)	3,965	2,036
Pension Adjustments, Amortization of Prior Service Cost
Pension adjustments:
Total before tax									476	477	377
Pension Adjustments, Amortization of Actuarial (Gain) Loss
Pension adjustments:
Total before tax									11,960	9,691	14,209
Pension Adjustments
Pension adjustments:
Total before tax									12,436	10,168	14,586
Tax									(4,353)	(3,559)	(5,105)
Total reclassifications (after tax)									8,083	6,609	9,481
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains (Losses) on Available for Sale Assets
Unrealized gains (losses) on available for sale assets:
Realized (gains) losses									(34,954)	10,285	9,478
Amortization of (discount) premium									(47)	(4,185)	(6,346)
Income before income taxes									(35,001)	6,100	3,132
Income tax expense from continuing operations									12,250	(2,135)	(1,096)
Net income									$ (22,751)	$ 3,965	$ 2,036

Investments - Summary of Fixed

Investments - Summary of Fixed Maturities Available for Sale by Component (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 14,995,101	$ 14,188,050
Gross Unrealized Gains	2,056,907	1,273,795
Gross Unrealized Losses	(82,683)	(215,984)
Fair Value	$ 16,969,325	$ 15,245,861
Percentage of Total Fixed Maturities	100.00%	100.00%
U.S. Government direct, guaranteed, and government-sponsored enterprises
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 390,646	$ 381,054
Gross Unrealized Gains	18,173	895
Gross Unrealized Losses	(1,373)	(9,151)
Fair Value	$ 407,446	$ 372,798
Percentage of Total Fixed Maturities	2.00%	3.00%
States, municipalities, and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 1,091,960	$ 1,284,605
Gross Unrealized Gains	127,890	126,850
Gross Unrealized Losses	(135)	(1,327)
Fair Value	$ 1,219,715	$ 1,410,128
Percentage of Total Fixed Maturities	7.00%	9.00%
Foreign governments
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 20,236	$ 21,701
Gross Unrealized Gains	1,782	1,438
Gross Unrealized Losses	0	(62)
Fair Value	$ 22,018	$ 23,077
Percentage of Total Fixed Maturities	0.00%	0.00%
Corporates
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 12,923,415	$ 11,983,092
Gross Unrealized Gains	1,819,119	1,086,748
Gross Unrealized Losses	(70,698)	(187,360)
Fair Value	$ 14,671,836	$ 12,882,480
Percentage of Total Fixed Maturities	87.00%	85.00%
Corporates | Financial
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 3,282,526	$ 2,963,584
Gross Unrealized Gains	475,961	285,037
Gross Unrealized Losses	(23,392)	(45,885)
Fair Value	$ 3,735,095	$ 3,202,736
Percentage of Total Fixed Maturities	22.00%	21.00%
Corporates | Utilities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 1,955,737	$ 1,875,946
Gross Unrealized Gains	369,406	249,701
Gross Unrealized Losses	(1,298)	(12,604)
Fair Value	$ 2,323,845	$ 2,113,043
Percentage of Total Fixed Maturities	14.00%	14.00%
Corporates | Energy
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 1,619,349	$ 1,542,426
Gross Unrealized Gains	226,140	127,989
Gross Unrealized Losses	(25,392)	(44,324)
Fair Value	$ 1,820,097	$ 1,626,091
Percentage of Total Fixed Maturities	11.00%	11.00%
Corporates | Other corporate sectors
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 6,065,803	$ 5,601,136
Gross Unrealized Gains	747,612	424,021
Gross Unrealized Losses	(20,616)	(84,547)
Fair Value	$ 6,792,799	$ 5,940,610
Percentage of Total Fixed Maturities	40.00%	39.00%
Collateralized debt obligations
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 59,150	$ 60,726
Gross Unrealized Gains	20,084	13,062
Gross Unrealized Losses	(7,653)	(10,285)
Fair Value	$ 71,581	$ 63,503
Percentage of Total Fixed Maturities	0.00%	0.00%
Other asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 144,520	$ 56,410
Gross Unrealized Gains	4,835	621
Gross Unrealized Losses	0	(337)
Fair Value	$ 149,355	$ 56,694
Percentage of Total Fixed Maturities	1.00%	0.00%
Redeemable preferred stocks
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 365,174	$ 400,462
Gross Unrealized Gains	65,024	44,181
Gross Unrealized Losses	(2,824)	(7,462)
Fair Value	$ 427,374	$ 437,181
Percentage of Total Fixed Maturities	3.00%	3.00%
Redeemable preferred stocks | Financial
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 336,621	$ 371,862
Gross Unrealized Gains	62,892	43,383
Gross Unrealized Losses	(2,727)	(7,218)
Fair Value	$ 396,786	$ 408,027
Percentage of Total Fixed Maturities	3.00%	3.00%
Redeemable preferred stocks | Utilities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 28,553	$ 28,600
Gross Unrealized Gains	2,132	798
Gross Unrealized Losses	(97)	(244)
Fair Value	$ 30,588	$ 29,154
Percentage of Total Fixed Maturities	0.00%	0.00%

Investments - Schedule of Fixed

Investments - Schedule of Fixed Maturities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fixed Maturities Available for Sale, Amortized Cost
Due in one year or less	$ 147,457
Due after one year through five years	682,932
Due after five years through ten years	1,397,473
Due after ten years through twenty years	4,701,591
Due after twenty years	7,861,000
Mortgage-backed and asset-backed securities	204,648
Cost or Amortized Cost	14,995,101	$ 14,188,050
Fixed Maturities Available for Sale, Fair Value
Due in one year or less	149,495
Due after one year through five years	720,186
Due after five years through ten years	1,567,972
Due after ten years through twenty years	5,519,917
Due after twenty years	8,789,769
Mortgage-backed and asset-backed securities	221,986
Total fixed maturities available for sale, Fair Value	$ 16,969,325	$ 15,245,861

Investments - Schedule of Analy

Investments - Schedule of Analysis of Investment Operations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Investment Income [Line Items]
Investment income, gross									$ 862,730	$ 820,581	$ 786,542
Less investment expense									(14,845)	(13,678)	(12,591)
Net investment income	$ 212,955	$ 213,872	$ 212,776	$ 208,282	$ 205,488	$ 202,720	$ 201,642	$ 197,053	847,885	806,903	773,951
Fixed maturities available for sale
Net Investment Income [Line Items]
Investment income, gross									817,213	778,912	747,663
Policy loans
Net Investment Income [Line Items]
Investment income, gross									39,578	38,436	36,763
Other long-term investments
Net Investment Income [Line Items]
Investment income, gross									4,991	2,786	2,021
Short-term investments
Net Investment Income [Line Items]
Investment income, gross									$ 948	$ 447	$ 95

Investments - Realized Gain (Lo

Investments - Realized Gain (Loss) on Investments (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)	$ 17,469	$ 12,595	$ (705)	$ (5,748)	$ (18,463)	$ 3,482	$ 4,005	$ 293	$ 23,611	$ (10,683)	$ (8,791)
Applicable tax									(6,021)	3,739	3,077
Realized gains (losses) from investments, net of tax									17,590	(6,944)	(5,714)
Loss on redemption on debt
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)									(4,041)	0	0
Fixed maturities available for sale
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)									35,199	(10,645)	(9,479)
Fixed maturities available for sale | Other-than-temporary impairments
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)									(245)	0	0
Other investments
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses)									$ (7,302)	$ (38)	$ 688

Investments - Unrealized Gain (

Investments - Unrealized Gain (Loss) on Investments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gain (Loss) on Investments [Line Items]
Net change in unrealized gains (losses)	$ 921,421	$ 553,801	$ (1,166,032)
Fixed maturities available for sale
Gain (Loss) on Investments [Line Items]
Net change in unrealized gains (losses)	916,413	551,658	(1,163,295)
Other investments
Gain (Loss) on Investments [Line Items]
Net change in unrealized gains (losses)	$ 5,008	$ 2,143	$ (2,737)

Investments - Schedule of Selec

Investments - Schedule of Selected Information about Sales of Fixed Maturities (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales	$ 67,246,000	$ 340,434,000	$ 226,792,000
Fixed maturities available for sale
Schedule of Available-for-sale Securities [Line Items]
Proceeds from sales	67,246,000	358,285,000	226,792,000
Gross realized gains	5,079,000	6,133,000	259,000
Gross realized losses	(1,100,000)	(32,608,000)	(16,894,000)
Unsettled sales	$ 0	$ 17,900,000	$ 0

Investments - Assets Measured a

Investments - Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 16,969,325	$ 15,245,861
Percentage of total	100.00%	100.00%
U.S. Government direct, guaranteed, and government-sponsored enterprises
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 407,446	$ 372,798
States, municipalities, and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,219,715	1,410,128
Foreign governments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	22,018	23,077
Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	14,671,836	12,882,480
Collateralized debt obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	71,581	63,503
Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	149,355	56,694
Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	427,374	437,181
Financial | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,735,095	3,202,736
Financial | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	396,786	408,027
Utilities | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,323,845	2,113,043
Utilities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	30,588	29,154
Energy | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,820,097	1,626,091
Other corporate sectors | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	6,792,799	5,940,610
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 44	$ 45,302
Percentage of total	0.00%	0.30%
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Government direct, guaranteed, and government-sponsored enterprises
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 0	$ 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | States, municipalities, and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	44	45,302
Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign governments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Collateralized debt obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Financial | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Financial | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Utilities | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Utilities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Energy | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other corporate sectors | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 16,300,841	$ 14,577,456
Percentage of total	96.10%	95.60%
Significant Other Observable Inputs (Level 2) | U.S. Government direct, guaranteed, and government-sponsored enterprises
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 407,446	$ 372,798
Significant Other Observable Inputs (Level 2) | States, municipalities, and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,219,671	1,364,826
Significant Other Observable Inputs (Level 2) | Foreign governments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	22,018	23,077
Significant Other Observable Inputs (Level 2) | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	14,089,026	12,322,880
Significant Other Observable Inputs (Level 2) | Collateralized debt obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Significant Other Observable Inputs (Level 2) | Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	135,306	56,694
Significant Other Observable Inputs (Level 2) | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	427,374	437,181
Significant Other Observable Inputs (Level 2) | Financial | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	3,673,089	3,141,611
Significant Other Observable Inputs (Level 2) | Financial | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	396,786	408,027
Significant Other Observable Inputs (Level 2) | Utilities | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,168,115	1,959,143
Significant Other Observable Inputs (Level 2) | Utilities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	30,588	29,154
Significant Other Observable Inputs (Level 2) | Energy | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,779,281	1,598,976
Significant Other Observable Inputs (Level 2) | Other corporate sectors | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	6,468,541	5,623,150
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 668,440	$ 623,103
Percentage of total	3.90%	4.10%
Significant Unobservable Inputs (Level 3) | U.S. Government direct, guaranteed, and government-sponsored enterprises
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 0	$ 0
Significant Unobservable Inputs (Level 3) | States, municipalities, and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Foreign governments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	582,810	559,600
Significant Unobservable Inputs (Level 3) | Collateralized debt obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	71,581	63,503
Significant Unobservable Inputs (Level 3) | Other asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	14,049	0
Significant Unobservable Inputs (Level 3) | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Financial | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	62,006	61,125
Significant Unobservable Inputs (Level 3) | Financial | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Utilities | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	155,730	153,900
Significant Unobservable Inputs (Level 3) | Utilities | Redeemable preferred stocks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Energy | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	40,816	27,115
Significant Unobservable Inputs (Level 3) | Other corporate sectors | Corporates
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 324,258	$ 317,460

Investments - Schedule of Chang

Investments - Schedule of Changes in Assets Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Beginning Balance	$ 623,103	$ 601,188	$ 575,946
Included in realized gains/losses	0	788	1,182
Included in other comprehensive income	20,964	2,460	(560)
Acquisitions	35,666	33,662	38,600
Sales	0	0	0
Amortization	4,931	5,203	5,553
Other	(16,224)	(20,198)	(19,533)
Transfers into (out of) Level 3(2)	0	0	0
Ending Balance	668,440	623,103	601,188
Asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Beginning Balance	0	0	0
Included in realized gains/losses	0	0	0
Included in other comprehensive income	410	0	0
Acquisitions	14,000	0	0
Sales	0	0	0
Amortization	0	0	0
Other	(361)	0	0
Transfers into (out of) Level 3(2)	0	0	0
Ending Balance	14,049	0	0
Collateralized debt obligations
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Beginning Balance	63,503	70,382	63,232
Included in realized gains/losses	0	0	0
Included in other comprehensive income	9,654	(3,943)	11,365
Acquisitions	0	0	0
Sales	0	0	0
Amortization	4,914	5,186	5,536
Other	(6,490)	(8,122)	(9,751)
Transfers into (out of) Level 3(2)	0	0	0
Ending Balance	71,581	63,503	70,382
Corporates
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Beginning Balance	559,600	530,806	512,714
Included in realized gains/losses	0	788	1,182
Included in other comprehensive income	10,900	6,403	(11,925)
Acquisitions	21,666	33,662	38,600
Sales	0	0	0
Amortization	17	17	17
Other	(9,373)	(12,076)	(9,782)
Transfers into (out of) Level 3(2)	0	0	0
Ending Balance	$ 582,810	$ 559,600	$ 530,806

Investments - Quantitative Info

Investments - Quantitative Information about Level 3 Fair Value Measurements (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 16,969,325	$ 15,245,861
Collateralized debt obligations
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	71,581	63,503
Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	668,440	623,103
Significant Unobservable Inputs (Level 3) | Asset-backed securities | Determination of credit spread
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 14,049
Discount rate	5.35%
Significant Unobservable Inputs (Level 3) | Collateralized debt obligations
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 71,581	$ 63,503
Significant Unobservable Inputs (Level 3) | Collateralized debt obligations | Determination of credit spread
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	71,581
Significant Unobservable Inputs (Level 3) | Private placement fixed maturities | Determination of credit spread
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 582,810
Minimum | Significant Unobservable Inputs (Level 3) | Collateralized debt obligations | Determination of credit spread
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	7.00%
Minimum | Significant Unobservable Inputs (Level 3) | Private placement fixed maturities | Determination of credit spread
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	2.97%
Maximum | Significant Unobservable Inputs (Level 3) | Collateralized debt obligations | Determination of credit spread
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	8.25%
Maximum | Significant Unobservable Inputs (Level 3) | Private placement fixed maturities | Determination of credit spread
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	7.27%
Weighted Average | Significant Unobservable Inputs (Level 3) | Asset-backed securities | Determination of credit spread
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	5.35%
Weighted Average | Significant Unobservable Inputs (Level 3) | Collateralized debt obligations | Determination of credit spread
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	8.03%
Weighted Average | Significant Unobservable Inputs (Level 3) | Private placement fixed maturities | Determination of credit spread
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	3.93%

Investments - Transfers in and

Investments - Transfers in and Out of Each of the Valuation Levels of Fair Values (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quoted Prices in Active Markets for Identical Assets (Level 1)
Transfers In And Out Of Each Of The Valuation Levels Of Fair Values Of Investments[Line Items]
In	$ 42,372	$ 45,344	$ 17,252
Out	(597)	0	(49,744)
Net	41,775	45,344	(32,492)
Significant Other Observable Inputs (Level 2)
Transfers In And Out Of Each Of The Valuation Levels Of Fair Values Of Investments[Line Items]
In	597	0	49,744
Out	(42,372)	(45,344)	(17,252)
Net	(41,775)	(45,344)	32,492
Significant Unobservable Inputs (Level 3)
Transfers In And Out Of Each Of The Valuation Levels Of Fair Values Of Investments[Line Items]
In	0	0	0
Out	0	0	0
Net	$ 0	$ 0	$ 0

Investments - Additional Inform

Investments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)Issue	Dec. 31, 2016USD ($)Issue	Dec. 31, 2015USD ($)
Investment [Line Items]
Securities, cash and short-term investments held on deposit	$ 657,000,000	$ 600,000,000
Securities, cash and short-term investments held on deposit, at fair value	753,000,000	663,000,000
Written down securities carried at fair value	$ 59,000,000
Written down securities carried at fair value, percentage	0.40%
Gross unrealized loss	$ (82,683,000)	$ (215,984,000)
Decrease in unrealized loss position	$ 133,000,000
Total issues of fixed-maturities | Issue	1,502	1,565
Securities of state and municipal governments	7.00%
Percentage of invested assets rated below investment grade	4.00%
Par value of investment in fixed maturities rated below investment grade	$ 790,000,000
Amortized cost of investment in fixed maturities rated below investment grade	702,000,000
Fair value of investment in fixed maturities rated below investment grade	$ 679,000,000
TEXAS
Investment [Line Items]
State and municipal government securities at fair value invested by state	29.00%
OHIO
Investment [Line Items]
State and municipal government securities at fair value invested by state	9.00%
WASHINGTON
Investment [Line Items]
State and municipal government securities at fair value invested by state	8.00%
ILLINOIS
Investment [Line Items]
State and municipal government securities at fair value invested by state	7.00%
MICHIGAN
Investment [Line Items]
State and municipal government securities at fair value invested by state	5.00%
GEORGIA
Investment [Line Items]
State and municipal government securities at fair value invested by state	5.00%
OTHER STATES
Investment [Line Items]
Proportion of state and municipal government securities at fair value invested in selected states	5.00%
Fixed maturities available for sale
Investment [Line Items]
Other-than-temporary impairment	$ 245,000	$ 0	$ 0
Other-than-temporary impairment, net of tax	$ 159,000	$ 0	$ 0
Credit Concentration Risk
Investment [Line Items]
Concentration risk percentage	100.00%
Investment Portfolio | Credit Concentration Risk | Corporate Debt Securities and Redeemable Preferred Stock
Investment [Line Items]
Concentration risk percentage	85.00%

Investments - Schedule of Unrea

Investments - Schedule of Unrealized Investment Losses by Class of Investment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value
Fair Value, Less than Twelve Months	$ 498,363	$ 2,928,441
Fair Value, Twelve Months or Longer	605,288	647,528
Fair Value, Total	1,103,651	3,575,969
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(9,332)	(107,262)
Unrealized Loss Twelve Months or Longer	(73,351)	(108,722)
Unrealized Loss Total	(82,683)	(215,984)
Investment Grade
Fair Value
Fair Value, Less than Twelve Months	464,715	2,828,756
Fair Value, Twelve Months or Longer	354,546	313,064
Fair Value, Total	819,261	3,141,820
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(4,057)	(106,414)
Unrealized Loss Twelve Months or Longer	(11,154)	(31,657)
Unrealized Loss Total	(15,211)	(138,071)
Investment Grade | U.S. Government direct, guaranteed, and government-sponsored enterprises
Fair Value
Fair Value, Less than Twelve Months	34,388	321,133
Fair Value, Twelve Months or Longer	47,514	1,404
Fair Value, Total	81,902	322,537
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(422)	(8,553)
Unrealized Loss Twelve Months or Longer	(951)	(598)
Unrealized Loss Total	(1,373)	(9,151)
Investment Grade | States, municipalities, and political subdivisions
Fair Value
Fair Value, Less than Twelve Months	4,561	32,178
Fair Value, Twelve Months or Longer	1,771	683
Fair Value, Total	6,332	32,861
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(21)	(1,114)
Unrealized Loss Twelve Months or Longer	(9)	(19)
Unrealized Loss Total	(30)	(1,133)
Investment Grade | Foreign governments
Fair Value
Fair Value, Less than Twelve Months	0	4,416
Fair Value, Twelve Months or Longer	0	0
Fair Value, Total	0	4,416
Unrealized Loss
Unrealized Loss Less Than Twelve Months	0	(62)
Unrealized Loss Twelve Months or Longer	0	0
Unrealized Loss Total	0	(62)
Investment Grade | Corporates
Fair Value
Fair Value, Less than Twelve Months	425,766	2,423,674
Fair Value, Twelve Months or Longer	299,308	310,977
Fair Value, Total	725,074	2,734,651
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(3,614)	(96,104)
Unrealized Loss Twelve Months or Longer	(10,097)	(31,040)
Unrealized Loss Total	(13,711)	(127,144)
Investment Grade | Corporates | Financial
Fair Value
Fair Value, Less than Twelve Months	133,080	479,669
Fair Value, Twelve Months or Longer	35,302	64,335
Fair Value, Total	168,382	544,004
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(652)	(18,666)
Unrealized Loss Twelve Months or Longer	(1,429)	(4,627)
Unrealized Loss Total	(2,081)	(23,293)
Investment Grade | Corporates | Utilities
Fair Value
Fair Value, Less than Twelve Months	48,562	290,732
Fair Value, Twelve Months or Longer	32,345	16,977
Fair Value, Total	80,907	307,709
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(569)	(11,000)
Unrealized Loss Twelve Months or Longer	(729)	(1,604)
Unrealized Loss Total	(1,298)	(12,604)
Investment Grade | Corporates | Energy
Fair Value
Fair Value, Less than Twelve Months	23,463	83,064
Fair Value, Twelve Months or Longer	67,775	154,908
Fair Value, Total	91,238	237,972
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(81)	(1,076)
Unrealized Loss Twelve Months or Longer	(3,682)	(18,127)
Unrealized Loss Total	(3,763)	(19,203)
Investment Grade | Corporates | Metals and mining
Fair Value
Fair Value, Less than Twelve Months	0	5,936
Fair Value, Twelve Months or Longer	0	5,789
Fair Value, Total	0	11,725
Unrealized Loss
Unrealized Loss Less Than Twelve Months	0	(231)
Unrealized Loss Twelve Months or Longer	0	(187)
Unrealized Loss Total	0	(418)
Investment Grade | Corporates | Other corporate sectors
Fair Value
Fair Value, Less than Twelve Months	220,661	1,564,273
Fair Value, Twelve Months or Longer	163,886	68,968
Fair Value, Total	384,547	1,633,241
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(2,312)	(65,131)
Unrealized Loss Twelve Months or Longer	(4,257)	(6,495)
Unrealized Loss Total	(6,569)	(71,626)
Investment Grade | Other asset-backed securities
Fair Value
Fair Value, Less than Twelve Months	0	41,498
Fair Value, Twelve Months or Longer	0	0
Fair Value, Total	0	41,498
Unrealized Loss
Unrealized Loss Less Than Twelve Months	0	(337)
Unrealized Loss Twelve Months or Longer	0	0
Unrealized Loss Total	0	(337)
Investment Grade | Redeemable preferred stocks
Fair Value
Fair Value, Less than Twelve Months	0	5,857
Fair Value, Twelve Months or Longer	5,953	0
Fair Value, Total	5,953	5,857
Unrealized Loss
Unrealized Loss Less Than Twelve Months	0	(244)
Unrealized Loss Twelve Months or Longer	(97)	0
Unrealized Loss Total	(97)	(244)
Investment Grade | Redeemable preferred stocks | Utilities
Fair Value
Fair Value, Less than Twelve Months	0	5,857
Fair Value, Twelve Months or Longer	5,953	0
Fair Value, Total	5,953	5,857
Unrealized Loss
Unrealized Loss Less Than Twelve Months	0	(244)
Unrealized Loss Twelve Months or Longer	(97)	0
Unrealized Loss Total	(97)	(244)
Below Investment Grade
Fair Value
Fair Value, Less than Twelve Months	33,648	99,685
Fair Value, Twelve Months or Longer	250,742	334,464
Fair Value, Total	284,390	434,149
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(5,275)	(848)
Unrealized Loss Twelve Months or Longer	(62,197)	(77,065)
Unrealized Loss Total	(67,472)	(77,913)
Below Investment Grade | States, municipalities, and political subdivisions
Fair Value
Fair Value, Less than Twelve Months	200	0
Fair Value, Twelve Months or Longer	0	357
Fair Value, Total	200	357
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(105)	0
Unrealized Loss Twelve Months or Longer	0	(194)
Unrealized Loss Total	(105)	(194)
Below Investment Grade | Corporates
Fair Value
Fair Value, Less than Twelve Months	33,448	99,685
Fair Value, Twelve Months or Longer	214,019	304,481
Fair Value, Total	247,467	404,166
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(5,170)	(848)
Unrealized Loss Twelve Months or Longer	(51,817)	(59,368)
Unrealized Loss Total	(56,987)	(60,216)
Below Investment Grade | Corporates | Financial
Fair Value
Fair Value, Less than Twelve Months	0	0
Fair Value, Twelve Months or Longer	84,432	83,174
Fair Value, Total	84,432	83,174
Unrealized Loss
Unrealized Loss Less Than Twelve Months	0	0
Unrealized Loss Twelve Months or Longer	(21,311)	(22,592)
Unrealized Loss Total	(21,311)	(22,592)
Below Investment Grade | Corporates | Energy
Fair Value
Fair Value, Less than Twelve Months	8,114	15,567
Fair Value, Twelve Months or Longer	75,204	91,165
Fair Value, Total	83,318	106,732
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(104)	(385)
Unrealized Loss Twelve Months or Longer	(21,525)	(24,736)
Unrealized Loss Total	(21,629)	(25,121)
Below Investment Grade | Corporates | Metals and mining
Fair Value
Fair Value, Less than Twelve Months	0	32,478
Fair Value, Twelve Months or Longer	0	34,463
Fair Value, Total	0	66,941
Unrealized Loss
Unrealized Loss Less Than Twelve Months	0	(172)
Unrealized Loss Twelve Months or Longer	0	(2,023)
Unrealized Loss Total	0	(2,195)
Below Investment Grade | Corporates | Other corporate sectors
Fair Value
Fair Value, Less than Twelve Months	25,334	51,640
Fair Value, Twelve Months or Longer	54,383	95,679
Fair Value, Total	79,717	147,319
Unrealized Loss
Unrealized Loss Less Than Twelve Months	(5,066)	(291)
Unrealized Loss Twelve Months or Longer	(8,981)	(10,017)
Unrealized Loss Total	(14,047)	(10,308)
Below Investment Grade | Collateralized debt obligations
Fair Value
Fair Value, Less than Twelve Months	0	0
Fair Value, Twelve Months or Longer	12,347	9,714
Fair Value, Total	12,347	9,714
Unrealized Loss
Unrealized Loss Less Than Twelve Months	0	0
Unrealized Loss Twelve Months or Longer	(7,653)	(10,285)
Unrealized Loss Total	(7,653)	(10,285)
Below Investment Grade | Redeemable preferred stocks
Fair Value
Fair Value, Less than Twelve Months	0	0
Fair Value, Twelve Months or Longer	24,376	19,912
Fair Value, Total	24,376	19,912
Unrealized Loss
Unrealized Loss Less Than Twelve Months	0	0
Unrealized Loss Twelve Months or Longer	(2,727)	(7,218)
Unrealized Loss Total	(2,727)	(7,218)
Below Investment Grade | Redeemable preferred stocks | Financial
Fair Value
Fair Value, Less than Twelve Months	0	0
Fair Value, Twelve Months or Longer	24,376	19,912
Fair Value, Total	24,376	19,912
Unrealized Loss
Unrealized Loss Less Than Twelve Months	0	0
Unrealized Loss Twelve Months or Longer	(2,727)	(7,218)
Unrealized Loss Total	$ (2,727)	$ (7,218)

Investments - Schedule of Addit

Investments - Schedule of Additional Information about Investments in Unrealized Loss Position (Detail) - Issue	Dec. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Less than Twelve Months	92	407
Twelve Months or Longer	102	94
Total	194	501

Investments - Schedule of Other

Investments - Schedule of Other Long-Term Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investment [Line Items]
Other long-term investments	$ 108,559	$ 53,852
Investment in limited partnerships
Investment [Line Items]
Other long-term investments	66,522	51,509
Commercial mortgage participations
Investment [Line Items]
Other long-term investments	39,489	0
Other
Investment [Line Items]
Other long-term investments	$ 2,548	$ 2,343

Investments - Summary of Invest

Investments - Summary of Investment Portfolio (Detail) - Credit Concentration Risk	12 Months Ended
	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	100.00%
Other
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	1.00%
Fixed maturities available for sale | Corporates | Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	82.00%
Fixed maturities available for sale | Corporates | Below Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	3.00%
Fixed maturities available for sale | Securities of state and municipal governments | Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	7.00%
Fixed maturities available for sale | Government-sponsored enterprises | Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	2.00%
Fixed maturities available for sale | Other | Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	1.00%
Fixed maturities available for sale | Other | Below Investment Grade
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	1.00%
Policy loans
Schedule of Available-for-sale Securities [Line Items]
Concentration risk percentage	3.00%

Investments - Concentration of

Investments - Concentration of Credit Risk (Details)	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Insurance	16.00%
Electric utilities	12.00%
Oil and natural gas pipelines	7.00%
Banks	6.00%
Transportation	4.00%
Oil and natural gas exploration and production	4.00%
Chemicals	4.00%
Real estate investment trusts	4.00%
Food	3.00%
Metals and mining	3.00%

Deferred Acquisition Costs (Det

Deferred Acquisition Costs (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement Analysis of Deferred Policy Acquisition Costs
Balance at beginning of year				$ 3,783,158				$ 3,617,135	$ 3,783,158	$ 3,617,135	$ 3,457,397
Commissions									465,920	436,252	401,166
Other expenses									194,214	199,066	211,015
Total deferred									660,134	635,318	612,181
Foreign exchange adjustment									5,712	2,180	0
Adjustment attributable to unrealized investment losses									0	0	8,682
Total additions									665,846	637,498	620,863
Amortized during period	$ (120,040)	$ (122,334)	$ (122,121)	$ (125,908)	$ (116,191)	$ (116,821)	$ (117,245)	$ (118,806)	(490,403)	(469,063)	(445,625)
Foreign exchange adjustment									0	0	(15,500)
Adjustment attributable to unrealized investment gains									(538)	(2,412)	0
Total deductions									(490,941)	(471,475)	(461,125)
Balance at end of year	$ 3,958,063				$ 3,783,158				$ 3,958,063	$ 3,783,158	$ 3,617,135

Discontinued Operations - Addit

Discontinued Operations - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Discontinued Operations and Disposal Groups [Abstract]
Gain from sale of discontinued operations	$ 1.8
Gain from sale of discontinued operations, net of tax	$ 1.2

Discontinued Operations - Net A

Discontinued Operations - Net Assets Held For Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets:
Total assets related to discontinued operations	$ 68,520	$ 127,532
Liabilities:
Total liabilities related to discontinued operations	49,854	27,424
Amounts of contingent liabilities remaining		3,600
Medicare Part D
Assets:
Due premiums	3,945	8,840
Other receivables	64,575	118,692
Total assets related to discontinued operations	68,520	127,532
Liabilities:
Risk sharing payable	8,731	8,374
Current and deferred income taxes payable	1,077	3,820
Other	40,046	15,230
Total liabilities related to discontinued operations	49,854	27,424
Net assets	18,666	100,108
Centers for Medicare and Medicaid Services
Liabilities:
Amount payable to CSM	37,300
Centers for Medicare and Medicaid Services | Medicare Part D
Assets:
Other receivables	$ 65,000	50,000
Drug Manufacturers | Medicare Part D
Assets:
Other receivables		$ 69,000

Discontinued Operations - Incom

Discontinued Operations - Income from Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Benefits and expenses:
Gain from sale of discontinued operations										$ 1,800
Income from discontinued operations	$ (30)	$ (12)	$ (90)	$ (3,637)	$ 10,636	$ 9,959	$ (865)	$ (9,541)	$ (3,769)	10,189	$ 10,807
Income taxes paid									74,379	79,790	110,650
Medicare Part D
Revenue:
Health premium									0	222,840	260,657
Benefits and expenses:
Health policyholder benefits									3,827	183,423	213,114
Amortization of deferred acquisition costs									0	3,747	3,506
Commissions, premium taxes, and non-deferred acquisition expenses									763	16,396	20,909
Other operating expense									1,209	5,377	6,502
Total benefits and expenses									5,799	208,943	244,031
Income before income taxes for discontinued operations									(5,799)	13,897	16,626
Gain from sale of discontinued operations									0	1,779	0
Income taxes									2,030	(5,487)	(5,819)
Income from discontinued operations									(3,769)	10,189	10,807
Discontinued Operations | Medicare Part D
Benefits and expenses:
Income taxes paid									$ 714	$ 15,271	$ 3,409

Liability for Unpaid Claims - S

Liability for Unpaid Claims - Summary of Liability for Unpaid Health Claims (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Activity in the Liability for Unpaid Health Claims
Balance at beginning of year	$ 143,128	$ 137,120	$ 128,265
Incurred related to:
Current year	520,528	510,075	502,009
Prior years	(8,048)	(1,127)	(7,845)
Total incurred	512,480	508,948	494,164
Paid related to:
Current year	394,506	386,278	379,037
Prior years	114,237	116,662	106,272
Total paid	508,743	502,940	485,309
Balance at end of year	$ 146,865	$ 143,128	$ 137,120

Liability for Unpaid Claims -71

Liability for Unpaid Claims - Short-duration Contracts, Claims Development (Details) claim in Thousands, $ in Thousands	Dec. 31, 2017USD ($)claim	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 597,715
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	24,707
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	83,103	$ 83,119	$ 83,151	$ 82,644	$ 84,111
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Short-duration Insurance Contracts, Number of Reported Claims | claim	1,337
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 99,777	99,810	99,876	$ 101,407
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Short-duration Insurance Contracts, Number of Reported Claims | claim	1,600
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 141,259	141,460	$ 141,667
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 17
Short-duration Insurance Contracts, Number of Reported Claims | claim	2,224
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 138,899	$ 140,944
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 431
Short-duration Insurance Contracts, Number of Reported Claims | claim	2,158
Short-duration Insurance Contracts, Accident Year 2017 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 134,677
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 24,259
Short-duration Insurance Contracts, Number of Reported Claims | claim	1,765

Liability for Unpaid Claims -72

Liability for Unpaid Claims - Short-duration Contracts, Cumulative Paid Claims (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 573,008
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	24,707
Short-duration products	597,715
Short-duration Insurance Contracts, Accident Year 2013 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	83,103	$ 83,119	$ 83,131	$ 82,408	$ 68,159
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	0
Short-duration Insurance Contracts, Accident Year 2014 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	99,777	99,791	99,545	$ 81,054
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	0
Short-duration Insurance Contracts, Accident Year 2015 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	141,242	140,982	$ 115,922
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	17
Short-duration Insurance Contracts, Accident Year 2016 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	138,468	$ 114,720
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	431
Short-duration Insurance Contracts, Accident Year 2017 [Member]
Claims Development [Line Items]
Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	110,418
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 24,259

Liability for Unpaid Claims - R

Liability for Unpaid Claims - Reconciliation of Net Incurred and Paid Claims Development to Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration products	$ 597,715
Insurance lines other than short duration—life	186,429	$ 156,437
Total policy claims and other benefits payable	333,294	299,565
Health Insurance Product Line [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration products	24,707	26,721
Insurance lines other than short duration—health	122,158	116,407
Total policy claims and other benefits payable	$ 146,865	$ 143,128

Income Taxes - Components of In

Income Taxes - Components of Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax expense from continuing operations	$ (627,615)	$ 232,645	$ 249,894
Shareholders’ equity:
Other comprehensive income (loss)	318,475	186,206	(411,646)
Tax basis compensation expense (from the exercise of stock options and vesting of restricted stock awards) in excess of amounts recognized for financial reporting purposes	0	0	(17,577)
Income tax expense (benefit)	$ (309,140)	$ 418,851	$ (179,329)

Income Taxes - Income Taxes Exp

Income Taxes - Income Taxes Expense from Continuing Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current income tax (benefit) expense	$ 138,262	$ 132,806	$ 174,284
Deferred income tax (benefit) expense	(765,877)	99,839	75,610
Income tax expense (benefit) from continuing operations	$ (627,615)	$ 232,645	$ 249,894

Income Taxes - Summary of Effec

Income Taxes - Summary of Effective Income Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Expected income taxes	$ 290,727	$ 270,282	$ 268,165
Increase (reduction) in income taxes resulting from, amount:
Tax reform adjustment	(877,400)	0	0
Low income housing investments	(18,515)	(18,202)	(19,031)
Share-based awards	(19,549)	(18,653)	0
Other	(2,878)	(782)	760
Income tax expense (benefit) from continuing operations	$ (627,615)	$ 232,645	$ 249,894
Expected income taxes	35.00%	35.00%	35.00%
Increase (reduction) in income taxes resulting from, percent:
Tax reform adjustment	(105.60%)	0.00%	0.00%
Low income housing investments	(2.20%)	(2.40%)	(2.50%)
Share-based awards	(2.40%)	(2.40%)	(0.00%)
Other	(0.40%)	(0.10%)	0.10%
Income tax expense (benefit) from continuing operations	(75.60%)	30.10%	32.60%

Income Taxes - Significant Port

Income Taxes - Significant Portions of Deferred Tax Assets and Deferred Tax Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Fixed maturity investments	$ 8,692	$ 15,004
Carryover of tax losses	4,760	3,906
Total gross deferred tax assets	13,452	18,910
Deferred tax liabilities:
Unrealized gains	380,251	315,509
Employee and agent compensation	65,576	92,131
Deferred acquisition costs	618,889	975,873
Future policy benefits, unearned and advance premiums, and policy claims	248,752	391,451
Other liabilities	11,289	3,987
Total gross deferred tax liabilities	1,324,757	1,778,951
Net deferred tax liability	$ 1,311,305	$ 1,760,041

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	Dec. 22, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Reduction in deferred income tax expense related to one-time adjustment to reduce net deferred tax liability		$ 877,400,000	$ 0	$ 0
Reclassification from AOCI to retained earnings	$ 252,000,000
Operating loss carryforwards		22,700,000
Deferred tax assets, valuation allowance		0
Uncertain tax positions		0	0	0
Interest income, net of federal income tax expense		5,000	9,000	$ 11,000
Amount of accrued interest or penalties		$ 0	$ 0

Postretirement Benefits - Total

Postretirement Benefits - Total Cost of Retirement Plans Charged to Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Defined Contribution Plans	$ 4,145	$ 3,614	$ 3,429
Defined Benefit Pension Plans	$ 28,828	$ 24,202	$ 29,230

Postretirement Benefits - Addit

Postretirement Benefits - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)plan	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of nonqualified, noncontributory supplemental benefit pension plans | plan	2
Number of active noncontributory supplemental benefit pension plans | plan	1
Defined benefit plan contributions	$ 21,300,000	$ 15,800,000	$ 15,500,000
Maximum allowed investment percentage in any single issuer in pension plan assets at time of purchase	10.00%
Minimum
Defined Benefit Plan Disclosure [Line Items]
Contributions to benefit plans, future	$ 30,000,000
Maximum
Defined Benefit Plan Disclosure [Line Items]
Contributions to benefit plans, future	40,000,000
Capped eligible compensation	1,000,000
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan contributions	21,272,000	15,757,000
Nonqualified | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	75,000,000	69,000,000
Funded | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 466,000,000	$ 411,000,000

Postretirement Benefits - Activ

Postretirement Benefits - Activity for the SERP (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Premiums paid for insurance coverage	$ 2,050,000	$ 2,050,000	$ 10,068,000
Company owned life insurance	40,273,000	37,267,000
Exchange traded funds	55,442,000	48,999,000
Total investments of SERP	95,715,000	86,266,000
Cash deposited into investment fund		0	$ 0
Nonqualified | Active plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability	81,457,000	74,687,000
Nonqualified | Closed
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liability	$ 3,008,000	$ 3,220,000

Postretirement Benefits - Pensi

Postretirement Benefits - Pension Assets by Components at Fair Value (Detail) - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 377,624	$ 328,871	$ 307,596
Total percentage	100.00%	100.00%
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 173,356	$ 149,580
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	204,268	179,291
Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 180,506	$ 160,036
Total percentage	48.00%	49.00%
Corporate Bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 180,506	$ 160,036
Exchange Traded Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 164,351	$ 134,771
Total percentage	43.00%	41.00%
Exchange Traded Funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 164,351	$ 134,771
Other Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 256	$ 258
Total percentage	0.00%	0.00%
Other Bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 256	$ 258
Other long-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2,304
Total percentage	1.00%
Other long-term investments | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2,304
Guaranteed Annuity Contract
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 21,202	$ 18,997
Total percentage	6.00%	6.00%
Guaranteed Annuity Contract | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 21,202	$ 18,997
Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 3,984	$ 7,391
Total percentage	1.00%	2.00%
Short-term investments | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 3,984	$ 7,391
Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 5,021	$ 7,418
Total percentage	1.00%	2.00%
Other | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 5,021	$ 7,418
Financial | Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 43,451	$ 41,578
Total percentage	12.00%	13.00%
Financial | Corporate Bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 43,451	$ 41,578
Utilities | Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 46,144	$ 43,890
Total percentage	12.00%	13.00%
Utilities | Corporate Bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 46,144	$ 43,890
Energy | Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 25,023	$ 25,427
Total percentage	7.00%	8.00%
Energy | Corporate Bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 25,023	$ 25,427
Other corporate sectors | Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 65,888	$ 49,141
Total percentage	17.00%	15.00%
Other corporate sectors | Corporate Bonds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 65,888	$ 49,141

Postretirement Benefits - Weigh

Postretirement Benefits - Weighted Average Pension Plan Assumptions and Weighted Average Assumptions for Post-Retirement Benefit Plans Other Than Pensions (Detail) - Pension Benefits	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount Rate	3.75%	4.27%
Rate of Compensation Increase	4.37%	4.31%
Discount Rate	4.27%	4.64%	4.23%
Expected Long-Term Returns	6.96%	7.19%	6.96%
Rate of Compensation Increase	4.31%	4.33%	4.35%

Postretirement Benefits - Compo

Postretirement Benefits - Components of Net Periodic Pension Costs and Post-Retirement Benefit Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Net amortization	$ 12,436	$ 10,168	$ 14,586
Net periodic pension cost	28,828	24,202	29,230
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost—benefits earned during the period	17,942	15,502	15,902
Interest cost on projected benefit obligation	22,124	21,631	19,887
Expected return on assets	(23,597)	(23,127)	(21,204)
Net amortization	12,281	10,135	14,465
Recognition of actuarial loss	78	61	180
Net periodic pension cost	28,828	24,202	29,230
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost—benefits earned during the period	0	0	0
Interest cost on projected benefit obligation	1,132	1,139	1,075
Expected return on assets	0	0	0
Net amortization	155	33	120
Recognition of actuarial loss	167	(132)	367
Net periodic pension cost	$ 1,454	$ 1,040	$ 1,562

Postretirement Benefits - Analy

Postretirement Benefits - Analysis of Impact on Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Impact on Other Comprehensive Income
Balance at January 1	$ (173,883)	$ (152,149)	$ (152,999)
Amortization of prior service cost	476	477	377
Amortization of net actuarial (gain) loss	11,960	9,691	14,209
Total amortization	12,436	10,168	14,586
Plan amendments	0	0	(2,104)
Experience gain (loss)	(31,933)	(31,902)	(11,632)
Balance at December 31	(193,380)	(173,883)	(152,149)
Other Benefits
Defined Benefit Plan, Impact on Other Comprehensive Income
Balance at January 1	1,959
Total amortization	155	33	$ 120
Balance at December 31	$ 2,682	$ 1,959

Postretirement Benefits - Recon

Postretirement Benefits - Reconciliation of Benefit Obligation and Plan Assets, Pension Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in plan assets:
Contributions	$ 21,300	$ 15,800	$ 15,500
Pension Benefits
Changes in benefit obligation:
Obligation at beginning of year	527,522	476,581
Service cost	17,942	15,502	15,902
Interest cost	22,124	21,631	19,887
Plan amendments	0	0
Actuarial loss (gain)	55,369	34,667
Benefits paid	(20,351)	(20,859)
Obligation at end of year	602,606	527,522	476,581
Changes in plan assets:
Fair value at beginning of year	328,871	307,596
Return on assets	47,832	26,377
Contributions	21,272	15,757
Benefits paid	(20,351)	(20,859)
Fair value at end of year	377,624	328,871	307,596
Funded status at year end	(224,982)	(198,651)
Other Benefits
Changes in benefit obligation:
Obligation at beginning of year	23,721	22,479
Service cost	0	0	0
Interest cost	1,132	1,139	1,075
Actuarial loss (gain)	1,045	412
Benefits paid	(285)	(309)
Obligation at end of year	25,613	23,721	22,479
Changes in plan assets:
Fair value at beginning of year	0	0
Return on assets	0	0
Contributions	285	309
Benefits paid	(285)	(309)
Fair value at end of year	0	0	$ 0
Funded status at year end	$ (25,613)	$ (23,721)

Postretirement Benefits - Sched

Postretirement Benefits - Schedule of Amounts Recognized in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net amounts recognized at year end	$ (193,380)	$ (173,883)	$ (152,149)	$ (152,999)
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net loss (gain)	186,563	167,313
Prior service cost	4,135	4,611
Net amounts recognized at year end	190,698	171,924
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net loss (gain)	2,682	1,959
Net amounts recognized at year end	$ 2,682	$ 1,959

Postretirement Benefits - Porti

Postretirement Benefits - Portion of Other Comprehensive Income Expected to Be Reflected in Pension Expense in Next Year (Detail) - Pension Benefits $ in Thousands	Dec. 31, 2017USD ($)
Postretirement Benefits [Abstract]
Amortization of prior service cost	$ 476
Amortization of net actuarial loss	14,543
Total	$ 15,019

Postretirement Benefits - Estim

Postretirement Benefits - Estimated Future Payments for Pension Benefits and Other Postretirement Benefit Plans (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
2,018	$ 20,375
2,019	22,143
2,020	23,840
2,021	25,239
2,022	27,090
2023-2027	160,075
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
2,018	1,228
2,019	1,278
2,020	1,311
2,021	1,344
2,022	1,386
2023-2027	$ 7,515

Postretirement Benefits - Wei90

Postretirement Benefits - Weighted Average Assumptions for Post-Retirement Benefit Plans Other Than Pensions (Details) - Other Benefits	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount Rate	3.76%	4.29%
Discount Rate	4.29%	4.66%	4.23%

Supplemental Disclosures of C91

Supplemental Disclosures of Cash Flow Information - Summary of Noncash Transactions (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Stock-based compensation not involving cash	$ 37,034	$ 26,326	$ 28,664
Commitments for low-income housing interests	33,846	56,818	68,949
Exchanges of fixed maturity investments	84,312	224,901	0
Net unsettled security trades	$ 0	$ 15,020	$ 0

Supplemental Disclosures of C92

Supplemental Disclosures of Cash Flow Information - Summary of Amount Paid (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Interest paid	$ 82,494	$ 81,338	$ 74,792
Income taxes paid	$ 74,379	$ 79,790	$ 110,650

Debt - Selected Information abo

Debt - Selected Information about Debt Issues (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Outstanding Principal (Par Value)	$ 1,151,384
Outstanding Principal (Book Value)	1,136,576	$ 1,135,040
Outstanding Principal (Fair Value)	1,232,767
Less current maturity of term loan, par value	4,375
Less current maturity of term loan, book value	4,375	1,875
Less current maturity of term loan, fair value	4,375
Total long-term debt, par value	1,147,009
Long-term debt	1,132,201	1,133,165
Total long-term debt, fair value	1,228,392	1,233,019
Total short-term debt, par value	328,625
Total short-term debt, book value	328,067	264,475
Total short-term debt, fair value	328,067
Total debt, par value	1,475,634
Total debt, book value	1,460,268	1,397,640
Total debt, fair value	1,556,459
Commercial Paper
Debt Instrument [Line Items]
Total short-term debt, par value	324,250
Total short-term debt, book value	323,692	262,600
Total short-term debt, fair value	$ 323,692
Notes, Due 5/15/23
Debt Instrument [Line Items]
Debt instrument, maturity date	May 15, 2023
Annual Interest Rate	7.875%
Issue Date	1993-05
Outstanding Principal (Par Value)	$ 165,612
Outstanding Principal (Book Value)	164,284	164,095
Outstanding Principal (Fair Value)	$ 195,786
Senior Notes, Due 6/15/19
Debt Instrument [Line Items]
Debt instrument, maturity date	Jun. 15, 2019
Annual Interest Rate	9.25%
Issue Date	2009-06
Outstanding Principal (Par Value)	$ 292,647
Outstanding Principal (Book Value)	291,888	291,424
Outstanding Principal (Fair Value)	$ 320,697
Senior Notes, Due 9/15/22
Debt Instrument [Line Items]
Debt instrument, maturity date	Sep. 15, 2022
Annual Interest Rate	3.80%
Issue Date	2012-09
Outstanding Principal (Par Value)	$ 150,000
Outstanding Principal (Book Value)	148,477	148,189
Outstanding Principal (Fair Value)	$ 155,000
Junior Subordinated Debentures Due 12/15/52
Debt Instrument [Line Items]
Debt instrument, maturity date	Dec. 15, 2052
Annual Interest Rate	5.875%
Issue Date	2012-09
Outstanding Principal (Par Value)	$ 0
Outstanding Principal (Book Value)	0	120,929
Outstanding Principal (Fair Value)	$ 0
Junior Subordinated Debentures Due 3/15/36
Debt Instrument [Line Items]
Debt instrument, maturity date	Mar. 15, 2036
Annual Interest Rate	4.888%
Outstanding Principal (Par Value)	$ 20,000
Outstanding Principal (Book Value)	20,000	20,000
Outstanding Principal (Fair Value)	$ 20,000
Junior Subordinated Debentures Due 3/15/36 | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread	3.30%
Junior Subordinated Debentures Due 6/15/56
Debt Instrument [Line Items]
Debt instrument, maturity date	Jun. 15, 2056
Annual Interest Rate	6.125%
Issue Date	2016-04
Outstanding Principal (Par Value)	$ 300,000
Outstanding Principal (Book Value)	290,460	290,403
Outstanding Principal (Fair Value)	$ 321,120
Junior Subordinated Debentures Due 11/17/57
Debt Instrument [Line Items]
Annual Interest Rate	5.275%
Outstanding Principal (Par Value)	$ 125,000
Outstanding Principal (Book Value)	123,342	0
Outstanding Principal (Fair Value)	$ 122,039
Term Loan Due 5/17/21
Debt Instrument [Line Items]
Debt instrument, maturity date	May 17, 2021
Annual Interest Rate	2.60%
Issue Date	2016-06
Outstanding Principal (Par Value)	$ 98,125
Outstanding Principal (Book Value)	98,125	$ 100,000
Outstanding Principal (Fair Value)	$ 98,125
Term Loan Due 5/17/21 | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread	1.25%

Debt - Amount of Debt Due in Ne

Debt - Amount of Debt Due in Next Five Years (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Debt Disclosure [Abstract]
2,018	$ 328,625
2,019	299,522
2,020	9,375
2,021	77,500
2,022	150,000
Thereafter	$ 610,612

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	Nov. 17, 2017	Apr. 05, 2016	Dec. 31, 2017	May 17, 2016
Debt Instrument [Line Items]
Debt, face amount			$ 1,475,634,000
Term Loan Due 5/17/21
Debt Instrument [Line Items]
Interest rate			2.60%
Junior Subordinated Debentures Due 11/17/57 | Junior Subordinated Debt
Debt Instrument [Line Items]
Debt, face amount	$ 125,000,000
Interest rate	5.275%
Proceeds from issuance of subordinated long-term debt	$ 123,300,000
Junior Subordinated Debentures Due 11/17/57 | Senior Notes
Debt Instrument [Line Items]
Debt, face amount	$ 125,000,000
Interest rate	5.875%
Accrued interest	$ 143,000
Junior Subordinated Debentures due 2056 | Junior Subordinated Debt
Debt Instrument [Line Items]
Debt, face amount		$ 300,000,000
Interest rate		6.125%
Proceeds from issuance of subordinated long-term debt		$ 290,000,000
Senior Notes Due 6/15/2016 | Senior Notes
Debt Instrument [Line Items]
Debt, face amount		$ 250,000,000
Interest rate		6.375%
Accrued interest		$ 8,000,000
Term Loan Due 5/17/21 | Unsecured Debt
Debt Instrument [Line Items]
Debt, face amount				$ 100,000,000
Balloon payment				75,000,000
Line of Credit | $750 Million Credit Facility | Unsecured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 750,000,000
London Interbank Offered Rate (LIBOR) | Term Loan Due 5/17/21
Debt Instrument [Line Items]
Basis spread			1.25%

Debt - Short-Term Borrowings (D

Debt - Short-Term Borrowings (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Balance at end of period (at par value)	$ 1,475,634
Annualized interest rate	1.78%	0.96%
Letters of credit outstanding	$ 177,000	$ 177,000
Remaining amount available under credit line	248,750	310,150
Average balance outstanding during period	$ 323,429	$ 301,550	$ 350,851
Daily-weighted average interest rate (annualized)	1.30%	0.83%	0.43%
Maximum daily amount outstanding during period	$ 455,912	$ 412,676	$ 458,110
Short-term Debt
Short-term Debt [Line Items]
Balance at end of period (at par value)	$ 324,250	$ 262,850

Shareholders' Equity - Summary

Shareholders' Equity - Summary of Preferred and Common Share Activity (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Increase (Decrease) in Stockholders' Equity
Common stock issued, beginning balance	127,218,183
Treasury stock, beginning balance	(9,187,075)
Grants of restricted stock	169,870	186,961	193,788
Vesting of performance shares	153,360	306,802	287,390
Issuance of common stock due to exercise of stock options	1,661,808	2,184,169	1,576,485
Retirement of treasury stock	3,000,000	3,000,000	4,000,000
Common stock issued, ending balance	124,218,183	127,218,183
Treasury stock, ending balance	(9,625,104)	(9,187,075)
Preferred Stock
Increase (Decrease) in Stockholders' Equity
Preferred stock issued, beginning balance	0	0	0
Treasury stock, beginning balance	0	0	0
Preferred stock issued, ending balance	0	0	0
Treasury stock, ending balance	0	0	0
Common Stock
Increase (Decrease) in Stockholders' Equity
Common stock issued, beginning balance	127,218,183	130,218,183	134,218,183
Treasury stock, beginning balance	(9,187,075)	(7,848,231)	(6,287,907)
Grants of restricted stock	9,135	12,549	6,648
Forfeitures of restricted stock		0	(13,950)
Issuance of common stock due to exercise of stock options	1,661,808	2,184,169	1,576,485
Treasury stock acquired	(5,228,868)	(6,694,582)	(7,340,794)
Retirement of treasury stock	3,000,000	3,000,000	4,000,000
Common stock issued, ending balance	124,218,183	127,218,183	130,218,183
Treasury stock, ending balance	(9,625,104)	(9,187,075)	(7,848,231)
Performance Shares
Increase (Decrease) in Stockholders' Equity
Grants of restricted stock	153,000	167,500	179,500
Performance Shares | Common Stock
Increase (Decrease) in Stockholders' Equity
Vesting of performance shares	119,896	159,020	211,287

Shareholders' Equity - Addition

Shareholders' Equity - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Capitalization, Equity [Line Items]
Retirement of treasury stock	3,000,000	3,000,000	4,000,000
Dividends paid by subsidiaries to parent company	$ 454,000	$ 438,000	$ 466,000
Maximum amount of dividends expected to be available from subsidiaries without regulatory approval during next year	315,000
Restricted net assets	940,000
Retained earnings restricted by lenders' covenants	3,500,000
Retained earnings	$ 4,806,208	$ 3,890,798
Anti-dilutive shares	0	0	0
Stock Repurchase Plan
Schedule of Capitalization, Equity [Line Items]
Shares repurchased	4,100,000	5,200,000	6,300,000
Share repurchases under stock repurchase program, amount	$ 325,000	$ 311,000	$ 359,000
Stock Repurchase Plan for Anti-Dilutive Effect
Schedule of Capitalization, Equity [Line Items]
Shares repurchased	1,100,000	1,500,000	1,000,000
Share repurchases under stock repurchase program, amount	$ 88,000	$ 93,000	$ 60,000

Shareholders' Equity - Reconcil

Shareholders' Equity - Reconciliation of Basic and Diluted Weighted Average Shares Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Basic weighted average shares outstanding	116,342,529	120,001,191	125,094,628
Weighted average dilutive options outstanding	2,640,965	2,366,594	1,662,607
Diluted weighted average shares outstanding	118,983,494	122,367,785	126,757,235

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Grant Contract and Vesting Periods (Details) - Equity Option	12 Months Ended
	Dec. 31, 2017
Directors | Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contract Period	7 years
Directors | Director | 6 months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	100.00%
Employee 7 Year Grants | Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contract Period	7 years
Employee 7 Year Grants | Employee | 6 months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	0.00%
Employee 7 Year Grants | Employee | Yr 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	0.00%
Employee 7 Year Grants | Employee | Yr 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	50.00%
Employee 7 Year Grants | Employee | Yr 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	50.00%
Employee 10 Year Grants | Employee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contract Period	10 years
Employee 10 Year Grants | Employee | 6 months
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	0.00%
Employee 10 Year Grants | Employee | Yr 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	0.00%
Employee 10 Year Grants | Employee | Yr 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	25.00%
Employee 10 Year Grants | Employee | Yr 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	25.00%
Employee 10 Year Grants | Employee | Yr 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	25.00%
Employee 10 Year Grants | Employee | Yr 5
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage	25.00%

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - shares	Feb. 21, 2017	Feb. 24, 2016	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive plan, shares available for grant			2,964,320	2,964,320	5,088,461	6,872,282	8,458,593
Number of equity awards settled for cash				0
Restricted stock units outstanding			120,326,000	120,326,000	112,591,000	105,679,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Settlement of performance shares	119,896	159,020
Minimum | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance shares target distribution			0	0	0
Maximum | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance shares target distribution			306,000	306,000	335,000
Employee | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			5 years
Director | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			6 months
Director | Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			6 months
Directors | Director | Equity Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contract Period			7 years
Contract period			7 years
Employee 7 Year Grants | Employee | Equity Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contract Period			7 years
Employee 10 Year Grants | Employee | Equity Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contract Period			10 years
Contract period			10 years

Stock-Based Compensation - Anal

Stock-Based Compensation - Analysis of Shares Available for Grant (Detail)	12 Months Ended
	Dec. 31, 2017shares	Dec. 31, 2016shares	Dec. 31, 2015shares
Activity by Share-based Payment Award
Balance at January 1 (in shares)	5,088,461	6,872,282	8,458,593
Options expired and forfeited during year (in shares)	26,488	8,518	90,371
Restricted stock expired and forfeited during year (in shares)	46,500	0	89,745
Balance at December 31 (in shares)	2,964,320	5,088,461	6,872,282
Stock Options
Activity by Share-based Payment Award
Options granted during year (in shares)	(1,328,513)	(1,306,306)	(1,334,514)
Torchmark Corporation 2011 Incentive Plan | Restricted Stock, Restricted Stock Units And Performance Shares
Activity by Share-based Payment Award
Restricted stock, restricted stock units, and performance shares granted under the Torchmark Corporation 2011 Incentive Plan (in shares)	(868,616)	(486,033)	(431,913)
Minimum
Activity by Share-based Payment Award
Ratio by which each grant of stock options reduces shares available for grant	0.85
Ratio by which each grant of restricted stock reduces shares available for options	3.1
Maximum
Activity by Share-based Payment Award
Ratio by which each grant of stock options reduces shares available for grant	1
Ratio by which each grant of restricted stock reduces shares available for options	3.88

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock Compensation Activity (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation expense recognized	$ 37,034,000	$ 26,326,000	$ 28,664,000
Tax benefit recognized	32,511,000
Tax benefit recognized		27,867,000	10,033,000
Stock-based compensation expense capitalized	$ 0	$ 0	$ 0

Stock-Based Compensation - A104

Stock-Based Compensation - Additional Stock Compensation Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Unrecognized compensation	$ 31,309	$ 27,334
Weighted average period of expected recognition (in years)	10 months 10 days	10 months 21 days

Stock-Based Compensation - S105

Stock-Based Compensation - Summary of Options Outstanding (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	$ 29.59
Range of Exercise Prices, Maximum (in dollars per share)	$ 77.26
Options Outstanding, Number Outstanding (in shares)	6,753,801	6,973,591	7,734,841	7,889,321
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	4 years 10 months 21 days	4 years 8 months 12 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 53.59	$ 44.64	$ 38.84	$ 32.91
Options Exercisable, Number Exercisable (in shares)	2,928,979	3,115,847	3,774,061
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 43.79	$ 36.81	$ 29.37
$29.59 - $37.40
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	29.59
Range of Exercise Prices, Maximum (in dollars per share)	$ 37.4
Options Outstanding, Number Outstanding (in shares)	1,421,268
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	2 years 2 months 12 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 34.54
Options Exercisable, Number Exercisable (in shares)	1,366,689
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 34.42
50.64
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	50.64
Range of Exercise Prices, Maximum (in dollars per share)	$ 50.64
Options Outstanding, Number Outstanding (in shares)	1,405,725
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	6 years 4 months 21 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 50.64
Options Exercisable, Number Exercisable (in shares)	0
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 0
50.69 - 51.62
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	50.69
Range of Exercise Prices, Maximum (in dollars per share)	$ 51.62
Options Outstanding, Number Outstanding (in shares)	1,090,703
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	3 years 8 months 9 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 50.70
Options Exercisable, Number Exercisable (in shares)	958,463
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 50.70
53.61 - 56.32
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	53.61
Range of Exercise Prices, Maximum (in dollars per share)	$ 56.32
Options Outstanding, Number Outstanding (in shares)	1,384,582
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	4 years 7 months 17 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 53.65
Options Exercisable, Number Exercisable (in shares)	594,184
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 53.71
73.92 - 77.26
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	73.92
Range of Exercise Prices, Maximum (in dollars per share)	$ 77.26
Options Outstanding, Number Outstanding (in shares)	1,451,523
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	7 years 2 months 23 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 77.24
Options Exercisable, Number Exercisable (in shares)	9,643
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 73.92

Stock-Based Compensation - A106

Stock-Based Compensation - Analysis of Option Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Options
Options Outstanding-beginning of year (in shares)	6,973,591	7,734,841	7,889,321
Options Exercised (in shares)	(1,661,808)	(2,184,169)	(1,576,485)
Options Expired and forfeited (in shares)	(26,488)	(8,518)	(95,621)
Options Outstanding-end of year (in shares)	6,753,801	6,973,591	7,734,841
Options Exercisable at end of year (in shares)	2,928,979	3,115,847	3,774,061
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price [Abstract]
Outstanding-beginning of year, weighted average exercise price (in dollars per share)	$ 44.64	$ 38.84	$ 32.91
Options exercised in the period - weighted average exercise price (in dollars per share)	36.84	28.08	22.81
Options expired and forfeited in the period - weighted average exercise price (in dollars per share)	57.94	39.35	48.85
Outstanding-end of year, weighted average exercise price (in dollars per share)	53.59	44.64	38.84
Exercisable at end of year, weighted average exercise price (in dollars per share)	$ 43.79	$ 36.81	$ 29.37
7-year term
Options
Options Granted (in shares)	933,286	834,212	1,220,751
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price [Abstract]
Options granted in the period- weighted average exercise price (in dollars per share)	$ 77.19	$ 50.78	$ 53.62
10-year term
Options
Options Granted (in shares)	535,220	597,225	296,875
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price [Abstract]
Options granted in the period- weighted average exercise price (in dollars per share)	$ 77.26	$ 50.64	$ 53.61

Stock-Based Compensation - S107

Stock-Based Compensation - Summary of Additional Information of Stock Option Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted-average remaining contractual term (in years)	4 years 10 months 21 days	4 years 8 months 12 days
Aggregate intrinsic value	$ 231,277	$ 87,286
Weighted-average remaining contractual term (in years)	2 years 11 months 27 days	2 years 11 months 16 days
Aggregate intrinsic value	$ 137,424	$ 63,395

Stock-Based Compensation - Sele

Stock-Based Compensation - Selected Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted-average grant-date fair value of options granted (in dollars per share)	$ 12.88	$ 9.04	$ 11.97
Intrinsic value of options exercised	$ 70,948	$ 73,995	$ 54,854
Cash received from options exercised	61,215	61,329	35,958
Actual tax benefit received	$ 24,832	$ 25,898	$ 24,470

Stock-Based Compensation - S109

Stock-Based Compensation - Schedule of Additional Information on Unvested Options (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average remaining contractual term (in years)	4 years 10 months 21 days	4 years 8 months 12 days
Aggregate intrinsic value	$ 231,277	$ 87,286
Unvested Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding (in shares)	3,824,822	3,857,744
Weighted-average exercise price (in dollars per share)	$ 61.10	$ 50.97
Weighted-average remaining contractual term (in years)	6 years 4 months 2 days	6 years 1 month 10 days
Aggregate intrinsic value	$ 113,246	$ 23,891

Stock-Based Compensation - S110

Stock-Based Compensation - Summary of Restricted Stock and Restricted Stock Units Granted (Detail) - USD ($) $ / shares in Units, $ in Thousands	Feb. 27, 2018	Feb. 21, 2017	Feb. 24, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares (in shares)				169,870	186,961	193,788
Assumed adjustment for performance objectives (in shares)				106,084	(35,073)	(58,056)
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Settlement of performance shares		119,896	159,020
Shares (in shares)				153,000	167,500	179,500
Price per share (in dollars per share)				$ 77.26	$ 50.64	$ 53.61
Assumed adjustment for performance objectives (in shares)				106,084	(35,073)	(58,056)
Aggregate value				$ 11,821	$ 8,482	$ 9,623
Percent vested				0.00%	0.00%	0.00%
Executive Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares (in shares)				0	0	0
Price per share (in dollars per share)				$ 0
Assumed adjustment for performance objectives (in shares)
Directors Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares (in shares)				9,135	12,549	6,648
Price per share (in dollars per share)				$ 73.92	$ 57.39	$ 54.16
Assumed adjustment for performance objectives (in shares)
Aggregate value				$ 675	$ 720	$ 360
Percent vested				100.00%	85.00%	100.00%
Directors Restricted Stock Units Including Dividend Equivalents
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares (in shares)				7,735	6,912	7,640
Price per share (in dollars per share)				$ 74.45	$ 56.74	$ 54.44
Aggregate value				$ 576	$ 392	$ 416
Percent vested				100.00%	100.00%	100.00%
Subsequent Event | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Settlement of performance shares	149,898

Stock-Based Compensation - A111

Stock-Based Compensation - Analysis of Unvested Restricted Stock (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Beginning Balance (in shares)	491,768	646,682	819,790
Grants (in shares)	169,870	186,961	193,788
Additional performance shares	106,084	(35,073)	(58,056)
Restriction lapses (in shares)	(153,360)	(306,802)	(287,390)
Forfeitures (in shares)	(15,000)	0	(21,450)
Ending Balance (in shares)	599,362	491,768	646,682
Executive Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Beginning Balance (in shares)	57,450	187,665	263,430
Grants (in shares)	0	0	0
Additional performance shares
Restriction lapses (in shares)	(14,700)	(130,215)	(61,815)
Forfeitures (in shares)	(7,500)	0	(13,950)
Ending Balance (in shares)	35,250	57,450	187,665
Executive Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Beginning Balance (in shares)	432,424	459,017	556,360
Grants (in shares)	153,000	167,500	179,500
Additional performance shares	106,084	(35,073)	(58,056)
Restriction lapses (in shares)	(119,896)	(159,020)	(211,287)
Forfeitures (in shares)	(7,500)	0	(7,500)
Ending Balance (in shares)	564,112	432,424	459,017
Directors Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Beginning Balance (in shares)	1,894	0	0
Grants (in shares)	9,135	12,549	6,648
Additional performance shares
Restriction lapses (in shares)	(11,029)	(10,655)	(6,648)
Forfeitures (in shares)
Ending Balance (in shares)	0	1,894	0
Directors Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Beginning Balance (in shares)	0	0	0
Grants (in shares)	7,735	6,912	7,640
Additional performance shares
Restriction lapses (in shares)	(7,735)	(6,912)	(7,640)
Forfeitures (in shares)
Ending Balance (in shares)	0	0	0

Stock-Based Compensation - S112

Stock-Based Compensation - Schedule of Weighted-Average Grant-Date Fair Value of Unvested Restricted Stock (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Executive Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Grant-date fair value per share at January 1, 2016 (in dollars per share)	$ 38.46
Grants (in dollars per share)	0
Restriction lapses (in dollars per share)	(30.69)
Forfeitures (in dollars per share)	(37.40)
Grant-date fair value per share at December 31, 2016 (in dollars per share)	41.93	$ 38.46
Executive Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Grant-date fair value per share at January 1, 2016 (in dollars per share)	49.79
Grants (in dollars per share)	77.26
Estimated additional performance shares (in dollars per share)	71.76
Restriction lapses (in dollars per share)	(72.42)
Forfeitures (in dollars per share)	(43.85)
Grant-date fair value per share at December 31, 2016 (in dollars per share)	56.64	49.79
Directors Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Grant-date fair value per share at January 1, 2016 (in dollars per share)	63.39
Grants (in dollars per share)	73.92	57.39	$ 54.16
Restriction lapses (in dollars per share)	(72.11)
Grant-date fair value per share at December 31, 2016 (in dollars per share)		$ 63.39
Directors Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares
Grants (in dollars per share)	73.92
Restriction lapses (in dollars per share)	$ (73.92)

Business Segments - Schedule of

Business Segments - Schedule of Segment Premium Revenue by Each Marketing Groups (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Amount	$ 3,282,935	$ 3,137,034	$ 2,998,720
% of Total	100.00%	100.00%	100.00%
United American Independent
Segment Reporting Information [Line Items]
Amount	$ 376,690	$ 368,786	$ 360,501
% of Total	12.00%	12.00%	12.00%
Liberty National Exclusive
Segment Reporting Information [Line Items]
Amount	$ 470,842	$ 472,274	$ 480,263
% of Total	14.00%	15.00%	16.00%
American Income Exclusive
Segment Reporting Information [Line Items]
Amount	$ 1,088,315	$ 997,737	$ 911,242
% of Total	33.00%	32.00%	30.00%
Family Heritage Exclusive
Segment Reporting Information [Line Items]
Amount	$ 256,727	$ 238,941	$ 223,425
% of Total	8.00%	8.00%	8.00%
Direct Response
Segment Reporting Information [Line Items]
Amount	$ 886,375	$ 853,158	$ 816,303
% of Total	27.00%	27.00%	27.00%
Other
Segment Reporting Information [Line Items]
Amount	$ 203,986	$ 206,138	$ 206,986
% of Total	6.00%	6.00%	7.00%
Life
Segment Reporting Information [Line Items]
Amount	$ 2,306,547	$ 2,189,333	$ 2,073,065
% of Total	100.00%	100.00%	100.00%
Life | United American Independent
Segment Reporting Information [Line Items]
Amount	$ 12,547	$ 13,733	$ 15,036
% of Total	1.00%	1.00%	1.00%
Life | Liberty National Exclusive
Segment Reporting Information [Line Items]
Amount	$ 274,635	$ 270,476	$ 271,113
% of Total	12.00%	12.00%	13.00%
Life | American Income Exclusive
Segment Reporting Information [Line Items]
Amount	$ 999,279	$ 913,355	$ 830,903
% of Total	43.00%	42.00%	40.00%
Life | Family Heritage Exclusive
Segment Reporting Information [Line Items]
Amount	$ 3,193	$ 2,866	$ 2,334
% of Total	0.00%	0.00%	0.00%
Life | Direct Response
Segment Reporting Information [Line Items]
Amount	$ 812,907	$ 782,765	$ 746,693
% of Total	35.00%	36.00%	36.00%
Life | Other
Segment Reporting Information [Line Items]
Amount	$ 203,986	$ 206,138	$ 206,986
% of Total	9.00%	9.00%	10.00%
Health
Segment Reporting Information [Line Items]
Amount	$ 976,373	$ 947,663	$ 925,520
% of Total	100.00%	100.00%	100.00%
Health | United American Independent
Segment Reporting Information [Line Items]
Amount	$ 364,128	$ 355,015	$ 345,330
% of Total	37.00%	38.00%	37.00%
Health | Liberty National Exclusive
Segment Reporting Information [Line Items]
Amount	$ 196,207	$ 201,798	$ 209,150
% of Total	20.00%	21.00%	23.00%
Health | American Income Exclusive
Segment Reporting Information [Line Items]
Amount	$ 89,036	$ 84,382	$ 80,339
% of Total	9.00%	9.00%	9.00%
Health | Family Heritage Exclusive
Segment Reporting Information [Line Items]
Amount	$ 253,534	$ 236,075	$ 221,091
% of Total	26.00%	25.00%	24.00%
Health | Direct Response
Segment Reporting Information [Line Items]
Amount	$ 73,468	$ 70,393	$ 69,610
% of Total	8.00%	7.00%	7.00%
Annuity
Segment Reporting Information [Line Items]
Amount	$ 15	$ 38	$ 135
% of Total	100.00%	100.00%	100.00%
Annuity | United American Independent
Segment Reporting Information [Line Items]
Amount	$ 15	$ 38	$ 135
% of Total	100.00%	100.00%	100.00%

Business Segments - Additional

Business Segments - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Loss Contingencies [Line Items]
Number of segments | segment	4
Administrative settlements	$ 8,659,000	$ 3,795,000	$ 1,394,000
Administrative settlement, after tax	5,600,000	$ 2,500,000	$ 906,000
Guarantee liability	0
One-time increase in stock-based compensation expense due to Tax Reform	3,380,000
One-time increase in stock-based compensation expense due to Tax Reform, net of tax	2,200,000
Insurance-related assessments
Loss Contingencies [Line Items]
Guarantee liability	9,600,000
Guaranty liability, recoverable amount	$ 1,800,000

Business Segments - Reconciliat

Business Segments - Reconciliation of Segment Operating Information to Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Premium	$ 826,473	$ 819,217	$ 816,614	$ 820,631	$ 787,908	$ 783,411	$ 785,855	$ 779,860	$ 3,282,935	$ 3,137,034	$ 2,998,720
Net investment income	212,955	213,872	212,776	208,282	205,488	202,720	201,642	197,053	847,885	806,903	773,951
Other income									1,142	1,375	2,185
Total revenue									4,131,962	3,945,312	3,774,856
Expenses:
Policy benefits	562,465	551,219	556,415	557,776	540,138	532,152	531,485	524,973	2,227,875	2,128,748	2,016,212
Policy reserves									0	0	0
Deferred acquisition costs									0	0	0
Amortization of acquisition costs	120,040	122,334	122,121	125,908	116,191	116,821	117,245	118,806	490,403	469,063	445,625
Commissions, premium taxes, and non-deferred acquisition costs									264,860	249,174	237,541
Insurance administrative expense									210,590	197,151	186,191
Parent expense									9,631	8,587	9,003
Stock-based compensation expense									37,034	26,326	28,664
Stock-based compensation expense									3,380
Interest expense									84,532	83,345	76,642
Total benefits and expenses									3,324,925	3,162,394	2,999,878
Subtotal									807,037	782,918	774,978
Non-operating items									14,128	4,348	1,394
Measure of segment profitability (pretax)									821,165	787,266	776,372
Deduct applicable income taxes									(247,484)	(237,906)	(253,459)
Net operating income from continuing operations									573,681	549,360	522,913
Add (deduct) realized investment gains (losses)	17,469	12,595	(705)	(5,748)	(18,463)	3,482	4,005	293	23,611	(10,683)	(8,791)
Deduct guaranty fund assessments									(1,801)
Deduct increase in stock-based compensation expense due to Tax Legislation									(3,380)
Deduct administrative settlements									(8,659)	(3,795)	(1,394)
Deduct non-operating fees									(288)	(553)
Income before income taxes per Consolidated Statement of Operations	$ 216,371	$ 220,610	$ 201,926	$ 191,741	$ 175,982	$ 201,461	$ 199,344	$ 195,448	830,648	772,235	766,187
Operating Segments | Life
Revenue:
Premium									2,306,547	2,189,333	2,073,065
Total revenue									2,306,547	2,189,333	2,073,065
Expenses:
Policy benefits									1,549,602	1,475,477	1,374,608
Policy reserves									(607,007)	(577,827)	(552,298)
Deferred acquisition costs									186,236	178,946	172,947
Amortization of acquisition costs									396,268	374,499	353,595
Commissions, premium taxes, and non-deferred acquisition costs									177,111	164,476	154,811
Total benefits and expenses									1,702,210	1,615,571	1,503,663
Subtotal									604,337	573,762	569,402
Measure of segment profitability (pretax)									604,337	573,762	569,402
Operating Segments | Health
Revenue:
Premium									976,373	947,663	925,520
Total revenue									976,373	947,663	925,520
Expenses:
Policy benefits									628,640	612,725	602,610
Policy reserves									(77,792)	(73,382)	(69,057)
Deferred acquisition costs									23,454	23,060	22,760
Amortization of acquisition costs									96,519	90,385	83,341
Commissions, premium taxes, and non-deferred acquisition costs									86,044	84,819	81,489
Total benefits and expenses									756,865	737,607	721,143
Subtotal									219,508	210,056	204,377
Measure of segment profitability (pretax)									219,508	210,056	204,377
Operating Segments | Annuity
Revenue:
Premium									15	38	135
Total revenue									15	38	135
Expenses:
Policy benefits									35,836	36,751	38,994
Policy reserves									(49,571)	(51,131)	(53,295)
Deferred acquisition costs									690	807	1,138
Amortization of acquisition costs									2,466	4,179	8,689
Commissions, premium taxes, and non-deferred acquisition costs									32	38	41
Total benefits and expenses									(10,547)	(9,356)	(4,433)
Subtotal									10,562	9,394	4,568
Measure of segment profitability (pretax)									10,562	9,394	4,568
Operating Segments | Investment
Revenue:
Net investment income									847,885	806,903	773,951
Total revenue									847,885	806,903	773,951
Expenses:
Policy reserves									734,370	702,340	674,650
Deferred acquisition costs									(210,380)	(202,813)	(196,845)
Interest expense									84,532	83,345	76,642
Total benefits and expenses									608,522	582,872	554,447
Subtotal									239,363	224,031	219,504
Measure of segment profitability (pretax)									239,363	224,031	219,504
Operating Segments | Corporate & Other
Revenue:
Other income									1,270	1,534	2,379
Total revenue									1,270	1,534	2,379
Expenses:
Insurance administrative expense									210,590	196,598	186,191
Parent expense									9,631	8,587	9,003
Stock-based compensation expense									33,654	26,326	28,664
Total benefits and expenses									253,875	231,511	223,858
Subtotal									(252,605)	(229,977)	(221,479)
Measure of segment profitability (pretax)									(252,605)	(229,977)	(221,479)
Adjustments
Revenue:
Other income									(128)	(159)	(194)
Total revenue									(128)	(159)	(194)
Expenses:
Policy benefits									13,797	3,795
Amortization of acquisition costs									(4,850)
Commissions, premium taxes, and non-deferred acquisition costs									1,673	(159)	1,200
Insurance administrative expense										553
Stock-based compensation expense									3,380
Total benefits and expenses									14,000	4,189	1,200
Subtotal									(14,128)	(4,348)	(1,394)
Non-operating items									14,128		1,394
Measure of segment profitability (pretax)									0	$ 0	$ 0
Deduct increase in stock-based compensation expense due to Tax Legislation									$ (3,380)

Business Segments - Assets by S

Business Segments - Assets by Segment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting, Asset Reconciling Item [Line Items]
Cash and invested assets	$ 17,853,047	$ 15,955,891
Accrued investment income	233,453	223,148
Deferred acquisition costs	3,958,063	3,783,158	$ 3,617,135	$ 3,457,397
Goodwill	441,591	441,591
Other assets	988,831	1,032,299
Total assets	23,474,985	21,436,087
Life
Segment Reporting, Asset Reconciling Item [Line Items]
Deferred acquisition costs	3,423,296	3,261,220
Goodwill	309,609	309,609
Total assets	3,732,905	3,570,829
Health
Segment Reporting, Asset Reconciling Item [Line Items]
Deferred acquisition costs	529,068	512,701
Goodwill	131,982	131,982
Total assets	661,050	644,683
Annuity
Segment Reporting, Asset Reconciling Item [Line Items]
Deferred acquisition costs	5,699	9,237
Total assets	5,699	9,237
Investment
Segment Reporting, Asset Reconciling Item [Line Items]
Cash and invested assets	17,853,047	15,955,891
Accrued investment income	233,453	223,148
Total assets	18,086,500	16,179,039
Other
Segment Reporting, Asset Reconciling Item [Line Items]
Other assets	988,831	1,032,299
Total assets	$ 988,831	$ 1,032,299

Business Segments - Other Balan

Business Segments - Other Balances by Segment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	$ 13,439,472	$ 12,825,837
Unearned and advance premiums	61,430	64,017
Policy claims and other benefits payable	333,294	299,565
Debt	1,460,268	1,397,640
Other	1,949,100	2,282,167
Total	17,243,564	16,869,226
Life
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	10,353,286	9,825,776
Unearned and advance premiums	16,927	16,828
Policy claims and other benefits payable	186,429	156,437
Total	10,556,642	9,999,041
Health
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	1,831,338	1,706,870
Unearned and advance premiums	44,503	47,189
Policy claims and other benefits payable	146,865	143,128
Total	2,022,706	1,897,187
Annuity
Segment Reporting, Other Significant Reconciling Item [Line Items]
Future policy benefits	1,254,848	1,293,191
Total	1,254,848	1,293,191
Investment
Segment Reporting, Other Significant Reconciling Item [Line Items]
Debt	1,460,268	1,397,640
Total	1,460,268	1,397,640
Other
Segment Reporting, Other Significant Reconciling Item [Line Items]
Other	1,949,100	2,282,167
Total	$ 1,949,100	$ 2,282,167

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)guaranteestatelease	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Obligation with Joint and Several Liability Arrangement [Line Items]
Retention limits per life	$ 2,000,000
Percentage of insurance ceded on total life insurance in force (less than)	0.40%
Ratio of reinsurance ceded to premium income	0.20%
Life reinsurance assumed ratio to life insurance in force	1.80%
Reinsurance assumed ratio on premium income	0.70%	0.70%	0.80%
Rental expense	$ 6,446,000	$ 6,520,000	$ 6,722,000
Number of guarantee arrangements | guarantee	4
Guarantee liability	$ 0
Letters of credit facility outstanding	$ 177,000,000	$ 177,000,000
Number of states private entities contracted with to conduct audits | state	47
Letter of Credit
Obligation with Joint and Several Liability Arrangement [Line Items]
Letter of credit maximum available amount	$ 250,000,000
Equipment Lease Guarantees
Obligation with Joint and Several Liability Arrangement [Line Items]
Number of leases under guarantee | lease	3
Maximum exposure under guarantees	$ 10,000,000
Flight Equipment | Equipment Lease Guarantees
Obligation with Joint and Several Liability Arrangement [Line Items]
Number of leases under guarantee | lease	2
Software, Furniture and Equipment | Equipment Lease Guarantees
Obligation with Joint and Several Liability Arrangement [Line Items]
Number of leases under guarantee | lease	1
Commercial mortgage participations
Obligation with Joint and Several Liability Arrangement [Line Items]
Purchase commitment of private placement fixed maturities	$ 210,000,000
Insurance-related assessments
Obligation with Joint and Several Liability Arrangement [Line Items]
Guarantee liability	9,600,000
Guaranty Liabilities, Recoverable Amount	7,800,000
Guaranty liability, recoverable amount	$ 1,800,000

Commitments and Contingencie119

Commitments and Contingencies - Schedule of Future Minimum Rental Commitments (Details) $ in Thousands	Dec. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 3,483
2,019	3,298
2,020	3,124
2,021	2,886
2,022	1,943
Thereafter	$ 1,830

Commitments and Contingencie120

Commitments and Contingencies - Low-Income Housing Commitments (Details) $ in Thousands	Dec. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 27,326
2,019	9,198
2,020	3,257
2,021	2,213
2,022	2,169
Thereafter	$ 246,836

Selected Quarterly Data (Una121

Selected Quarterly Data (Unaudited) - Schedule of Selected Quarterly Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Premium income	$ 826,473	$ 819,217	$ 816,614	$ 820,631	$ 787,908	$ 783,411	$ 785,855	$ 779,860	$ 3,282,935	$ 3,137,034	$ 2,998,720
Net investment income	212,955	213,872	212,776	208,282	205,488	202,720	201,642	197,053	847,885	806,903	773,951
Realized investment gains (losses)	17,469	12,595	(705)	(5,748)	(18,463)	3,482	4,005	293	23,611	(10,683)	(8,791)
Total revenue	1,056,899	1,046,015	1,029,078	1,023,581	975,345	989,773	991,884	977,627	4,155,573	3,934,629	3,766,065
Policyholder benefits	562,465	551,219	556,415	557,776	540,138	532,152	531,485	524,973	2,227,875	2,128,748	2,016,212
Amortization of deferred acquisition costs	120,040	122,334	122,121	125,908	116,191	116,821	117,245	118,806	490,403	469,063	445,625
Pretax income from continuing operations	216,371	220,610	201,926	191,741	175,982	201,461	199,344	195,448	830,648	772,235	766,187
Income from continuing operations	1,027,376	153,346	140,363	137,178	124,812	141,910	139,294	133,574	1,458,263	539,590	516,293
Income from discontinued operations	(30)	(12)	(90)	(3,637)	10,636	9,959	(865)	(9,541)	(3,769)	10,189	10,807
Net income	$ 1,027,346	$ 153,334	$ 140,273	$ 133,541	$ 135,448	$ 151,869	$ 138,429	$ 124,033	$ 1,454,494	$ 549,779	$ 527,100
Basic net income per common share:
Continuing operations (in dollars per share)	$ 8.93	$ 1.32	$ 1.20	$ 1.16	$ 1.05	$ 1.19	$ 1.16	$ 1.10	$ 12.53	$ 4.50	$ 4.13
Discontinued operations (in dollars per share)	0	0	0	(0.03)	0.09	0.08	(0.01)	(0.08)	(0.03)	0.08	0.08
Total basic net income per common share (in dollars per share)	8.93	1.32	1.20	1.13	1.14	1.27	1.15	1.02	12.50	4.58	4.21
Diluted net income per common share:
Continuing operations (in dollars per share)	8.71	1.29	1.18	1.14	1.03	1.16	1.13	1.08	12.26	4.41	4.07
Discontinued operations (in dollars per share)	0	0	0	(0.03)	0.09	0.09	0	(0.07)	(0.04)	0.08	0.09
Total diluted net income per common share (in dollars per share)	$ 8.71	$ 1.29	$ 1.18	$ 1.11	$ 1.12	$ 1.25	$ 1.13	$ 1.01	$ 12.22	$ 4.49	$ 4.16

Schedule II. Condensed Finan122

Schedule II. Condensed Financial Information of Registrant (Condensed Balance Sheets) (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets:
Short-term investments	$ 127,071	$ 72,040
Total investments	17,734,484	15,879,728
Cash	118,563	76,163	$ 61,383	$ 66,019
Other assets	528,536	520,313
Total assets	23,474,985	21,436,087
Liabilities:
Short-term debt	328,067	264,475
Long-term debt	1,132,201	1,133,165
Other liabilities	489,609	413,760
Total liabilities	17,243,564	16,869,226
Shareholders' equity:
Preferred stock	0	0
Common stock	124,218	127,218
Additional paid-in capital	508,476	490,421
Accumulated other comprehensive income	1,424,274	577,574
Retained earnings	4,806,208	3,890,798
Treasury stock	(631,755)	(519,150)
Total shareholders’ equity	6,231,421	4,566,861	4,055,552	4,697,466
Total liabilities and shareholders’ equity	23,474,985	21,436,087
Parent Company
Assets:
Long-term investments	35,562	33,586
Short-term investments	5,624	0
Total investments	41,186	33,586
Cash	1,008	0	$ 0	$ 0
Investment in affiliates	7,763,704	6,004,429
Due from affiliates	95,920	96,005
Taxes receivable from affiliates	63,099	88,406
Other assets	135,616	119,801
Total assets	8,100,533	6,342,227
Liabilities:
Short-term debt	328,067	264,475
Long-term debt	1,281,971	1,282,891
Due to affiliates	8,002	0
Other liabilities	251,072	228,000
Total liabilities	1,869,112	1,775,366
Shareholders' equity:
Preferred stock	351	351
Common stock	124,218	127,218
Additional paid-in capital	858,987	840,932
Accumulated other comprehensive income	1,424,274	577,574
Retained earnings	4,806,208	3,890,798
Treasury stock	(982,617)	(870,012)
Total shareholders’ equity	6,231,421	4,566,861
Total liabilities and shareholders’ equity	$ 8,100,533	$ 6,342,227

Schedule II. Condensed Finan123

Schedule II. Condensed Financial Information of Registrant (Condensed Statements of Operations) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net investment income	$ 212,955	$ 213,872	$ 212,776	$ 208,282	$ 205,488	$ 202,720	$ 201,642	$ 197,053	$ 847,885	$ 806,903	$ 773,951
Realized investment gains (losses)	17,469	12,595	(705)	(5,748)	(18,463)	3,482	4,005	293	23,611	(10,683)	(8,791)
Total revenue	1,056,899	1,046,015	1,029,078	1,023,581	975,345	989,773	991,884	977,627	4,155,573	3,934,629	3,766,065
General operating expenses									257,255	232,064	223,858
Interest expense									84,532	83,345	76,642
Total benefits and expenses									3,324,925	3,162,394	2,999,878
Income before income taxes	216,371	220,610	201,926	191,741	175,982	201,461	199,344	195,448	830,648	772,235	766,187
Income taxes									627,615	(232,645)	(249,894)
Net income	$ 1,027,346	$ 153,334	$ 140,273	$ 133,541	$ 135,448	$ 151,869	$ 138,429	$ 124,033	1,454,494	549,779	527,100
Other comprehensive income (loss):
Comprehensive income (loss)									2,048,794	895,406	(238,405)
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net investment income									26,130	25,352	23,715
Realized investment gains (losses)									(2,791)	0	8
Total revenue									23,339	25,352	23,723
General operating expenses									61,447	52,613	54,100
Reimbursements from affiliates									(52,776)	(54,288)	(53,436)
Interest expense									88,474	86,853	79,677
Total benefits and expenses									97,145	85,178	80,341
Income before income taxes									(73,806)	(59,826)	(56,618)
Income taxes									(9,874)	23,479	15,542
Net operating loss before equity in earnings of affiliates									(83,680)	(36,347)	(41,076)
Equity in earnings of affiliates									1,538,174	586,126	568,176
Net income									1,454,494	549,779	527,100
Other comprehensive income (loss):
Attributable to Parent Company									(8,409)	(11,314)	(3,539)
Attributable to affiliates									602,709	356,941	(761,966)
Comprehensive income (loss)									$ 2,048,794	$ 895,406	$ (238,405)

Schedule II. Condensed Finan124

Schedule II. Condensed Financial Information of Registrant (Condensed Statement of Cash Flows) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net income	$ 1,027,346	$ 153,334	$ 140,273	$ 133,541	$ 135,448	$ 151,869	$ 138,429	$ 124,033	$ 1,454,494	$ 549,779	$ 527,100
Other, net									67,933	20,079	13,985
Cash provided from (used for) operating activities									1,429,058	1,398,708	1,120,050
Cash provided from (used for) investing activities:
Disposition of investments									559,623	578,004	606,690
Net decrease (increase) in short-term investments									(55,031)	(17,274)	(38,884)
Additions to properties									(20,285)	(25,162)	(36,957)
Cash provided from (used for) investing activities									(926,824)	(1,062,436)	(633,350)
Cash provided from (used for) financing activities:
Repayment of debt									(126,875)	(250,000)	0
Proceeds from issuance of debt									125,000	400,000	0
Payment for debt issuance costs									(1,661)	(9,638)	0
Net issuance (repayment) of commercial paper									61,092	22,224	1,978
Issuance of stock									61,215	61,329	35,958
Acquisitions of treasury stock									(412,989)	(404,784)	(418,526)
Excess tax benefit from stock option exercises									0	0	17,577
Payment of dividends									(68,831)	(66,931)	(66,899)
Cash provided from (used for) financing activities									(453,981)	(319,791)	(525,705)
Increase (decrease) in cash									42,400	14,780	(4,636)
Cash at beginning of year				76,163				61,383	76,163	61,383	66,019
Cash at end of year	118,563				76,163				118,563	76,163	61,383
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net income									1,454,494	549,779	527,100
Equity in earnings of affiliates									(1,538,174)	(586,126)	(568,176)
Cash dividends from subsidiaries									453,904	437,566	466,416
Other, net									52,957	(6,718)	20,371
Cash provided from (used for) operating activities									423,181	394,501	445,711
Cash provided from (used for) investing activities:
Net decrease (increase) in short-term investments									(5,624)	(3,466)	17,338
Investment in subsidiaries									(31,000)	(35,000)	(2)
Additions to properties									(7,230)	(21,965)	(468)
Loaned money to affiliates									(180,000)	(363,056)	(282,508)
Repayments from affiliates									180,000	318,056	282,508
Cash provided from (used for) investing activities									(43,854)	(105,431)	16,868
Cash provided from (used for) financing activities:
Repayment of debt									(126,875)	(250,000)	0
Proceeds from issuance of debt									125,000	400,000	0
Payment for debt issuance costs									(1,661)	(9,638)	0
Net issuance (repayment) of commercial paper									61,092	22,224	1,978
Issuance of stock									61,215	61,329	35,958
Acquisitions of treasury stock									(412,989)	(404,784)	(418,526)
Borrowed money from affiliate									278,500	60,000	15,000
Repayments to affiliates									(270,500)	(78,000)	(15,000)
Excess tax benefit from stock option exercises									0	0	8,180
Payment of dividends									(92,101)	(90,201)	(90,169)
Cash provided from (used for) financing activities									(378,319)	(289,070)	(462,579)
Increase (decrease) in cash									1,008	0	0
Cash at beginning of year				$ 0				$ 0	0	0	0
Cash at end of year	$ 1,008				$ 0				$ 1,008	$ 0	$ 0

Schedule II. Condensed Finan125

Schedule II. Condensed Financial Information of Registrant (Notes To Condensed Financial Statements) (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Dividends from subsidiaries	$ 454,000	$ 438,000	$ 466,000
Stock-based compensation not involving cash	37,034	26,326	28,664
Interest paid	82,494	81,338	74,792
Income taxes received	$ 74,379	$ 79,790	110,650
Preferred stock, shares outstanding	0	0
Parent Company
Condensed Financial Statements, Captions [Line Items]
Dividends from subsidiaries	$ 453,904	$ 437,566	466,416
Stock-based compensation not involving cash	37,034	26,326	28,664
Borrowed money from affiliate	0	0	56,503
Investment in subsidiaries	317,027	0	39,206
Borrowed money from affiliate	0	0	17,297
Interest paid	86,606	84,952	77,920
Income taxes received	$ (19,961)	$ (20,838)	$ (22,009)
Preferred stock, liquidation distribution available to stockholders, per share in thousands	$ 1,000
Preferred stock, liquidating distribution legally available, aggregate value	$ 351,000
Cumulative Series A Preferred Stock | Parent Company
Condensed Financial Statements, Captions [Line Items]
Preferred stock, shares issued	351,000
Preferred stock, shares outstanding	351,000
6.50% Cumulative Preferred Stock, Series A | Parent Company
Condensed Financial Statements, Captions [Line Items]
Preferred stock, shares issued	280,000
Preferred stock, shares outstanding	280,000
Preferred stock, dividend rate, percentage	6.50%
7.15% Cumulative Preferred Stock, Series A | Parent Company
Condensed Financial Statements, Captions [Line Items]
Preferred stock, shares issued	71,000
Preferred stock, shares outstanding	71,000
Preferred stock, dividend rate, percentage	7.15%

Schedule I. Reinsurance (Detail

Schedule I. Reinsurance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Life insurance in force, gross amount	$ 179,902,605	$ 174,314,897	$ 167,677,206
Life insurance in force, ceded to other companies	705,152	725,867	729,739
Life insurance in force, assumed from other companies	3,211,423	3,352,113	3,498,826
Life insurance in force, net amount	$ 182,408,876	$ 176,941,143	$ 170,446,293
Life insurance in force, percentage of amount assumed to net	1.80%	1.90%	2.10%
Premium, gross amount	$ 3,252,120	$ 3,103,835	$ 2,963,032
Premium, ceded to other companies	8,146	7,981	7,623
Premium, assumed from other companies	21,912	22,915	24,007
Premium, net amount	$ 3,265,886	$ 3,118,769	$ 2,979,416
Percentage of amount assumed to net	0.70%	0.70%	0.80%
Policy charges	$ 17,000	$ 18,300	$ 19,300
Life insurance
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Premium, gross amount	2,272,038	2,152,698	2,034,373
Premium, ceded to other companies	4,437	4,507	4,484
Premium, assumed from other companies	21,912	22,915	24,007
Premium, net amount	$ 2,289,513	$ 2,171,106	$ 2,053,896
Percentage of amount assumed to net	1.00%	1.10%	1.20%
Health insurance
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Premium, gross amount	$ 980,082	$ 951,137	$ 928,659
Premium, ceded to other companies	3,709	3,474	3,139
Premium, assumed from other companies	0	0	0
Premium, net amount	$ 976,373	$ 947,663	$ 925,520
Percentage of amount assumed to net	0.00%	0.00%	0.00%