Business Segments - Analysis of Profitability by Segment (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2016		Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015
Segment Reporting Information [Line Items]
Pretax operating income	$ 198,236		$ 193,869		$ 588,730		$ 582,337
Applicable taxes	(58,422)		(63,352)		(178,842)		(190,291)
Segment profits after tax	139,814		130,517		409,888		392,046
Discontinued operations (after tax)	9,959		11,528		(447)		(3,019)
After-tax total, after discontinued operations	149,773		142,045		409,441		389,027
Reconciling items, net of tax:
Realized gains (losses)	2,263		3,341		5,057		5,117
Non-operating fees	(167)		0		(167)		0
Net income	151,869	[1]	145,386	[2]	414,331	[1]	394,144	[2]
Operating Segments [Member] | Life insurance underwriting margin [Member]
Segment Reporting Information [Line Items]
Pretax operating income	143,141		144,100		431,045		424,880
Operating Segments [Member] | Health insurance underwriting margin [Member]
Segment Reporting Information [Line Items]
Pretax operating income	53,076		50,207		157,212		153,396
Operating Segments [Member] | Annuity underwriting margin [Member]
Segment Reporting Information [Line Items]
Pretax operating income	2,630		1,101		6,202		3,297
Operating Segments [Member] | Excessive investment income [Member]
Segment Reporting Information [Line Items]
Pretax operating income	56,738		53,906		166,008		165,696
Operating Segments [Member] | Other and corporate [Member]
Segment Reporting Information [Line Items]
Pretax operating income	(57,349)		(55,445)		(171,737)		(164,932)
Operating Segments [Member] | Other and corporate [Member] | Other income [Member]
Segment Reporting Information [Line Items]
Pretax operating income	199		737		1,086		2,201
Operating Segments [Member] | Other and corporate [Member] | Administrative expense [Member]
Segment Reporting Information [Line Items]
Pretax operating income	(49,248)		(47,169)		(146,129)		(138,594)
Operating Segments [Member] | Other and corporate [Member] | Corporate [Member]
Segment Reporting Information [Line Items]
Pretax operating income	$ (8,300)		$ (9,013)		$ (26,694)		$ (28,539)

[1] Due to the adoption of ASU 2016-09, certain balances related to excess tax benefits from stock compensation were adjusted prospectively as described in Note 2—New Accounting Standards.

[2] Certain prior year balances were adjusted to give effect to discontinued operations as described in Note 5—Discontinued Operations.