Other Comprehensive Income (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013
Reclassifications out of accumulated other comprehensive income (loss)
Other realized investment (gains) losses, net	$ (25,935)		$ 55,820	$ (91,829)		$ 64,900
Net investment income	(292,061)		(375,041)	(911,694)		(909,006)
Tax expense or benefit	(2,358)		(4,709)	(12,422)		(12,429)
Net of tax	(1,578)		(8,745)	(20,268)		(23,081)
Amount reclassified from accumulated other comprehensive income (loss)
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	(1,578)		(8,745)	(20,268)		(23,081)
Unrealized holding (gains) losses arising on fixed maturities, available-for-sale
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	(2,664)		(8,361)	(18,374)		(20,131)
Unrealized holding (gains) losses arising on fixed maturities, available-for-sale | Amount reclassified from accumulated other comprehensive income (loss)
Reclassifications out of accumulated other comprehensive income (loss)
Other realized investment (gains) losses, net	(4,099)		(12,863)	(28,268)		(30,971)
Total before tax	(4,099)		(12,863)	(28,268)		(30,971)
Tax expense or benefit	(1,435)		(4,502)	(9,894)		(10,840)
Net of tax	(2,664)		(8,361)	(18,374)		(20,131)
Unrealized holding (gains) losses arising on cash flow hedges
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	(1,716)		(384)	(4,696)		(2,950)
Unrealized holding (gains) losses arising on cash flow hedges | Amount reclassified from accumulated other comprehensive income (loss)
Reclassifications out of accumulated other comprehensive income (loss)
Net investment income	(2,639)		(591)	(7,224)		(4,539)
Total before tax	(2,639)		(591)	(7,224)		(4,539)
Tax expense or benefit	(923)		(207)	(2,528)		(1,589)
Net of tax	(1,716)		(384)	(4,696)		(2,950)
Amortization of employee benefit plan items
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	2,802		0	2,802		0
Amortization of employee benefit plan items | Amount reclassified from accumulated other comprehensive income (loss)
Reclassifications out of accumulated other comprehensive income (loss)
Prior service costs (benefits)	(542)	[1]		(542)	[1]
Actuarial losses (gains)	2,187	[1]		2,187	[1]
Settlement	2,666			2,666
Total before tax	4,311			4,311
Tax expense or benefit	1,509			1,509
Net of tax	$ 2,802			$ 2,802

[1] These accumulated other comprehensive income components are included in the computation of net periodic (benefit) cost of employee benefit plans (see Note 13 for additional details).