Other Comprehensive Income (Details 3) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2015		Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014
Reclassifications out of accumulated other comprehensive income (loss)
Other realized investment (gains) losses, net	$ (15,859)		$ (38,297)	$ (34,509)		$ (65,894)
Net investment income	(220,169)		(319,610)	(579,025)		(619,633)
Prior service costs (benefits)	(181)		(181)	(362)	[1]	(361)
Actuarial losses (gains)	3,115		607	6,229	[1]	1,214
Tax expense or benefit	(1,763)		(2,288)	(12,416)		(10,064)
Net of tax	(1,368)		(4,248)	(19,245)		(18,690)
Amount reclassified from accumulated other comprehensive income (loss)
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	(1,368)		(4,248)	(19,245)		(18,690)
Unrealized holding (gains) losses, net, arising on fixed maturities, available-for-sale
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	(1,916)		(1,645)	(20,232)		(15,710)
Unrealized holding (gains) losses, net, 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	(2,947)		(2,531)	(31,126)		(24,169)
Total before tax	(2,947)		(2,531)	(31,126)		(24,169)
Tax expense or benefit	(1,031)		(886)	(10,894)		(8,459)
Net of tax	(1,916)		(1,645)	(20,232)		(15,710)
Unrealized holding (gains) losses, net, arising on cash flow hedges
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	(1,359)		(2,603)	(2,827)		(2,980)
Unrealized holding (gains) losses, net, arising on cash flow hedges | Amount reclassified from accumulated other comprehensive income (loss)
Reclassifications out of accumulated other comprehensive income (loss)
Net investment income	(2,091)		(4,005)	(4,349)		(4,585)
Total before tax	(2,091)		(4,005)	(4,349)		(4,585)
Tax expense or benefit	(732)		(1,402)	(1,522)		(1,605)
Net of tax	(1,359)		(2,603)	(2,827)		(2,980)
Amortization of employee benefit plan items
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	1,907		0	3,814		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)	(181)	[1]	0			0
Actuarial losses (gains)	3,115	[1]	0			0
Total before tax	2,934		0	5,867		0
Tax expense or benefit	1,027		0	2,053		0
Net of tax	$ 1,907		$ 0	$ 3,814		$ 0

[1] These accumulated other comprehensive income components are included in the computation of net periodic (benefit) cost of employee benefit plans (see Note 10 for additional details).