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