Other Comprehensive Income (Details 2) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Before-tax amount
Unrealized holding gains (losses) arising during the period on available-for-sale fixed maturity investments		$ (494,336)	$ 261,039	$ (312,961)	$ 572,337
Unrealized holding gains (losses) arising during the period on cash flow hedges		(16,633)	3,010	522	3,894
Reclassification adjustment for (gains) losses realized in net income		(5,038)	(6,536)	(35,475)	(28,754)
Net unrealized gains (losses) related to investments		(516,007)	257,513	(347,914)	547,477
Future policy benefits, DAC and VOBA adjustments		79,587	(29,720)	44,458	(86,968)
Net unrealized gains (losses)		(436,420)	227,793	(303,456)	460,509
Employee benefit plan adjustment		2,934	0	5,537	0
Other comprehensive (loss) income before income taxes		(433,486)	227,793	(297,919)	460,509
Tax (expense) benefit
Unrealized holding gains (losses) arising during the period on available-for-sale fixed maturity investments		173,018	(91,364)	109,537	(200,318)
Unrealized holding gains (losses) arising during the period on cash flow hedges		5,821	(1,054)	(183)	(1,363)
Reclassification adjustment for (gains) losses realized in net income		1,763	2,288	12,416	10,064
Net unrealized gains (losses)		180,602	(90,130)	121,770	(191,617)
Future policy benefits, DAC and VOBA adjustments		(27,855)	10,402	(15,560)	30,439
Net unrealized gains (losses)		152,747	(79,728)	106,210	(161,178)
Employee benefit plan adjustment		(1,027)		(1,938)
Other comprehensive income (loss)		151,720	(79,728)	104,272	(161,178)
Net-of-tax amount
Unrealized holding gains (losses) arising during the period on available-for-sale fixed maturity investments		(321,318)	169,675	(203,424)	372,019
Unrealized holding gains (losses) arising during the period on cash flow hedges		(10,812)	1,956	339	2,531
Reclassification adjustment for (gains) losses realized in net income		(3,275)	(4,248)	(23,059)	(18,690)
Net unrealized gains (losses)		(335,405)	167,383	(226,144)	355,860
Future policy benefits, DAC and VOBA adjustments		51,732	(19,318)	28,898	(56,529)
Net unrealized gains (losses)		(283,673)	148,065	(197,246)	299,331
Employee benefit plan adjustment		1,907		3,599
Other comprehensive income (loss)	[1]	$ (281,766)	$ 148,065	$ (193,647)	$ 299,331

[1] Other comprehensive (loss) income includes the non-credit component of impaired gains (losses), net, on fixed maturities available-for-sale in the amounts of $1,314 and $(4,588) for the three months ended June 30, 2015, and 2014, respectively, and $(1,229) and $(2,816) for the six months ended June 30, 2015, and 2014, respectively.