Other Comprehensive Income (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Before-tax amount
Unrealized gains (losses) arising during the year on fixed maturities, available-for-sale	$ (20,574)	[1]	$ 281,812	[1]	$ (650,447)	[1]	$ 488,870	[1]
Net changes during the year related to cash flow hedges	(49,908)		(8,578)		(33,000)		(1,539)
Reclassification adjustment for losses (gains) realized in net income	(13,454)		(26,467)		(35,510)		(69,234)
Net unrealized (losses) gains related to investments	(83,936)		246,767		(718,957)		418,097
Future policy benefits, DAC and VOBA adjustments	26,455		(78,023)		162,987		(106,646)
Net unrealized gains (losses)	(57,481)		168,744		(555,970)		311,451
Other comprehensive income (loss) before income taxes	(57,481)		168,744		(555,970)		311,451
Tax (expense) benefit
Unrealized gains (losses) arising during the year on fixed maturities, available-for-sale	7,201		(98,634)		227,656		(171,105)
Net changes during the year related to cash flow hedges	17,468		3,002		11,550		539
Reclassification adjustment for gains realized in net income	4,709		9,263		12,429		24,232
Net unrealized gains (losses)	29,378		(86,369)		251,635		(146,334)
Future policy benefits, deferred acquisition costs and value of business acquired adjustments	(9,261)		27,309		(57,046)		37,326
Net unrealized gains (losses)	20,117		(59,060)		194,589		(109,008)
Other comprehensive income (loss)	20,117		(59,060)		194,589		(109,008)
Net-of-tax amount
Unrealized gains (losses) arising during the year on fixed maturities, available-for-sale	(13,373)		183,178		(422,791)		317,765
Net changes during the year related to cash flow hedges	(32,440)		(5,576)		(21,450)		(1,000)
Reclassification adjustment for gains realized in net income	(8,745)		(17,204)		(23,081)		(45,002)
Net unrealized gains (losses)	(54,558)		160,398		(467,322)		271,763
Future policy benefits, deferred acquisition costs and value of business acquired adjustments	17,194		(50,714)		105,941		(69,320)
Net unrealized gains (losses)	(37,364)		109,684		(361,381)		202,443
Other comprehensive income (loss)	$ (37,364)		$ 109,684		$ (361,381)		$ 202,443

[1] Other comprehensive income (loss) includes the non-credit component of impaired losses on fixed maturities available-for-sale in the amounts of $3,173 and $9,218 for the three months ended September 30, 2013 and 2012, respectively, and $9,818 and $16,151 for the nine months ended September 30, 2013 and 2012, respectively.