Accumulated Other Comprehensive Income (Loss) - Details About AOCI Components (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2017		Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	$ (62,438)		$ (149,032)	$ (206,713)		$ (374,490)
Operating expenses	409,356		508,458	1,350,172		1,546,360
Provision (benefit) for income tax	60,132		(17,749)	18,034		(42,511)
Unrealized gains (losses) on investments
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	(64,136)	[1]	(150,482)	(211,281)	[1]	(379,974)	[1]
OTTI losses recognized in AOCI
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	1,746		1,497	4,712		5,618
Cash flow hedge
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	(48)		(47)	(144)		(134)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	0		0	0		0
Underfunded pension liability
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	0		0	0		0
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	(62,438)		(149,032)	(206,713)		(374,490)
Provision (benefit) for income tax	1,912		5,255	2,054		8,463
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(60,526)		(143,777)	(204,659)		(366,027)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized gains (losses) on investments
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments sold	(55,949)		(150,661)	(184,587)		(407,106)
OTTI on investments transferred to (from) OCI	3,598		10,019	11,632		64,977
Reclassification adjustment for investments transferred to equity method	0		(4,531)	0		(4,531)
Total before tax	(64,136)		(150,482)	(211,281)		(379,974)
Provision (benefit) for income tax	1,937		5,291	2,106		8,501
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(62,199)		(145,191)	(209,175)		(371,473)
Reclassification out of Accumulated Other Comprehensive Income [Member] | OTTI losses recognized in AOCI
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments sold	1,683		1,497	4,599		5,876
OTTI on investments transferred to (from) OCI	63		0	113		(258)
Total before tax	1,746		1,497	4,712		5,618
Provision (benefit) for income tax	(25)		(36)	(52)		(38)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	1,721		1,461	4,660		5,580
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash flow hedge
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	(48)		(47)	(144)		(134)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(48)		(47)	(144)		(134)
Life Funds Withheld Assets
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments sold	18,879		44,011	83,131		108,541
OTTI on investments transferred to (from) OCI	0		0	0		(2,598)
Life Funds Withheld Assets | Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized gains (losses) on investments
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Change in adjustments related to future policy benefit reserves, net of tax	$ (11,785)		$ (5,309)	$ (38,326)		$ (33,314)

[1] For certain annuity contracts that are subject to the GreyCastle Life Retro Arrangements, policy benefit reserves were historically increased for the impact of changes in unrealized gains on investments supporting such contracts as if the gains had been realized, with a corresponding entry to other comprehensive income ("Shadow Adjustments"). Upon completion of the GreyCastle Life Retro Arrangements, no further Shadow Adjustments were recorded. At December 31, 2016, the cumulative impact of the Shadow Adjustments was $212.1 million. During the nine months ended September 30, 2017, net movements of $(14.0) million were recorded, resulting in a total cumulative net impact of Shadow Adjustments on future policy benefit reserves of $198.1 million at September 30, 2017.