Segment and Geographical Information - Assets and Operations by Segment (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues		$ 383,626	$ 355,709	$ 1,125,221	$ 1,050,752
Income (loss) before income taxes		88,437	74,953	250,531	218,588
Assets		11,368,683		11,368,683		$ 10,610,783
Term Life Insurance Segment [Member]
Segment Reporting Information [Line Items]
Revenues		222,598	197,205	639,253	563,795
Income (loss) before income taxes		58,137	46,519	162,234	127,284
Assets		5,878,013		5,878,013		5,638,682
Investment and Savings Products Segment [Member]
Segment Reporting Information [Line Items]
Revenues		130,080	128,596	387,604	392,561
Income (loss) before income taxes		35,760	34,811	103,514	107,600
Assets	[1]	2,462,111		2,462,111		2,157,548
Corporate and Other Distributed Products Segment [Member]
Segment Reporting Information [Line Items]
Revenues		30,948	29,908	98,364	94,396
Income (loss) before income taxes		(5,460)	$ (6,377)	(15,217)	$ (16,296)
Assets		$ 3,028,559		$ 3,028,559		$ 2,814,553

[1] The Investment and Savings Products segment includes assets held in separate accounts. Excluding separate accounts, the Investment and Savings Products segment assets were approximately $114.4 million and $93.8 million as of September 30, 2016 and December 31, 2015, respectively.