Other Comprehensive Income (Details 3) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassifications out of accumulated other comprehensive income (loss)
Other realized investment (gains) losses, net	$ (42,013)	$ (15,859)	$ (73,819)	$ (34,509)
Net investment income	(355,755)	(220,169)	(687,540)	(579,025)
Interest expense	(8,679)	(9,645)	(18,403)	(19,282)
Amortization of unrecognized prior service costs (benefits)	(151)	(181)	(302)	(362)
Actuarial (gains)	2,385	3,115	4,770	6,229
Tax expense or benefit	(10,022)	(1,763)	(17,882)	(12,416)
Net of tax	(17,161)	(1,368)	(30,305)	(19,245)
Amount reclassified from accumulated other comprehensive income (loss)
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	(17,161)	(1,368)	(30,305)	(19,245)
Unrealized holding (gains) losses, net, arising on fixed maturities, available-for-sale
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	(17,337)	(1,916)	(30,317)	(20,232)
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	(26,672)	(2,947)	(46,642)	(31,126)
Total before tax	(26,672)	(2,947)	(46,642)	(31,126)
Tax expense or benefit	(9,335)	(1,031)	(16,325)	(10,894)
Net of tax	(17,337)	(1,916)	(30,317)	(20,232)
Unrealized holding (gains) losses, net, arising on cash flow hedges
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	(1,276)	(1,359)	(2,892)	(2,827)
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	(2,546)	(2,091)	(5,032)	(4,349)
Interest expense	583	0	583	0
Total before tax	(1,963)	(2,091)	(4,449)	(4,349)
Tax expense or benefit	(687)	(732)	(1,557)	(1,522)
Net of tax	(1,276)	(1,359)	(2,892)	(2,827)
Amortization of employee benefit plan items
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	1,452	1,907	2,904	3,814
Amortization of employee benefit plan items | Amount reclassified from accumulated other comprehensive income (loss)
Reclassifications out of accumulated other comprehensive income (loss)
Amortization of unrecognized prior service costs (benefits)	(151)	(181)	(302)	(362)
Actuarial (gains)	2,385	3,115	4,770	6,229
Settlement			0	0
Total before tax	2,234	2,934	4,468	5,867
Tax expense or benefit	782	1,027	1,564	2,053
Net of tax	$ 1,452	$ 1,907	$ 2,904	$ 3,814