Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Other Comprehensive Income [Roll Forward]
Beginning balance		$ 233,438	$ 603,018
Other comprehensive income (loss) before reclassifications		239,697	105,996
Amounts reclassified from AOCI		(13,144)	(17,877)
Other comprehensive income (loss)	[1]	226,553	88,119
Ending balance		459,991	691,137
Unrealized holding gains / losses arising on fixed maturities, available-for- sale
Other Comprehensive Income [Roll Forward]
Beginning balance		339,520	784,183
Other comprehensive income (loss) before reclassifications		290,296	117,894
Amounts reclassified from AOCI		(12,980)	(18,316)
Other comprehensive income (loss)		277,316	99,578
Ending balance		616,836	883,761
Unrealized holding gains / losses arising on cash flow hedges
Other Comprehensive Income [Roll Forward]
Beginning balance		45,284	33,141
Other comprehensive income (loss) before reclassifications		(1,043)	11,151
Amounts reclassified from AOCI		(1,616)	(1,468)
Other comprehensive income (loss)		(2,659)	9,683
Ending balance		42,625	42,824
Future policy benefits, DAC and VOBA adjustments
Other Comprehensive Income [Roll Forward]
Beginning balance		(65,785)	(108,194)
Other comprehensive income (loss) before reclassifications		(49,556)	(22,834)
Amounts reclassified from AOCI		0	0
Other comprehensive income (loss)		(49,556)	(22,834)
Ending balance		(115,341)	(131,028)
Employee benefit plan adjustment
Other Comprehensive Income [Roll Forward]
Beginning balance		(85,581)	(106,112)
Other comprehensive income (loss) before reclassifications		0	(215)
Amounts reclassified from AOCI		1,452	1,907
Other comprehensive income (loss)		1,452	1,692
Ending balance		$ (84,129)	$ (104,420)

[1] Other comprehensive income includes the non-credit component of impaired gains (losses), net, on fixed maturities available-for-sale in the amounts of $(1,895) and $(2,543) for the three months ended March 31, 2016, and 2015, respectively.