Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue:
Total premium	$ 853,979	$ 816,614	$ 1,704,085	$ 1,637,245
Net investment income	218,568	212,776	436,652	421,058
Realized investment gains (losses)	11,813	(705)	13,764	(6,453)
Other income	416	393	711	809
Total revenue	1,084,776	1,029,078	2,155,212	2,052,659
Benefits and expenses:
Life policyholder benefits	399,334	390,859	799,915	781,938
Health policyholder benefits	160,461	156,579	321,080	314,330
Other policyholder benefits	8,582	8,977	17,271	17,923
Total policyholder benefits	568,377	556,415	1,138,266	1,114,191
Amortization of deferred acquisition costs	129,077	122,121	258,697	248,029
Commissions, premium taxes, and non-deferred acquisition costs	69,427	65,032	139,066	130,148
Other operating expense	68,620	62,428	135,444	124,769
Interest expense	22,411	21,156	44,033	41,855
Total benefits and expenses	857,912	827,152	1,715,506	1,658,992
Income before income taxes	226,864	201,926	439,706	393,667
Income taxes	(42,471)	(61,563)	(81,602)	(116,126)
Income from continuing operations	184,393	140,363	358,104	277,541
Income (loss) from discontinued operations, net of tax	32	(90)	(79)	(3,727)
Net income	$ 184,425	$ 140,273	$ 358,025	$ 273,814
Basic net income (loss) per common share:
Continuing operations (in dollars per share)	$ 1.63	$ 1.20	$ 3.15	$ 2.37
Discontinued operations (in dollars per share)	0.00	0.00	0.00	(0.03)
Total basic net income per common share (in dollars per share)	1.63	1.20	3.15	2.34
Diluted net income (loss) per common share:
Continuing operations (in dollars per share)	1.59	1.18	3.08	2.32
Discontinued operations (in dollars per share)	0.00	0.00	0.00	(0.03)
Total diluted net income per common share (in dollars per share)	1.59	1.18	3.08	2.29
Dividends declared per common share (in dollars per share)	$ 0.16	$ 0.15	$ 0.32	$ 0.3
Life premium [Member]
Revenue:
Total premium	$ 602,534	$ 573,836	$ 1,200,837	$ 1,149,673
Health premium [Member]
Revenue:
Total premium	251,440	242,775	503,238	487,566
Other premium [Member]
Revenue:
Total premium	$ 5	$ 3	$ 10	$ 6