Other Comprehensive Income (Details 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassifications out of accumulated other comprehensive income (loss)
Other realized investment (gains) losses, net	$ 11,754	$ (31,806)
Net investment income	(313,471)	(331,785)
Interest expense	(7,630)	(9,724)
Amortization of unrecognized prior service costs (benefits)	73	(151)
Actuarial (gains)	2,073	2,385
Tax expense or benefit	516	(7,860)
Net of tax	2,354	(13,144)
Unrealized holding (gains) losses, net, arising on fixed maturities, available-for-sale
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	1,896	(12,980)
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	2,917	(19,970)
Total before tax	2,917	(19,970)
Tax expense or benefit	1,021	(6,990)
Net of tax	1,896	(12,980)
Unrealized holding (gains) losses, net, arising on cash flow hedges
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	(937)	(1,616)
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	(2,322)	(2,486)
Interest expense	880	0
Total before tax	(1,442)	(2,486)
Tax expense or benefit	(505)	(870)
Net of tax	(937)	(1,616)
Amortization of employee benefit plan items
Reclassifications out of accumulated other comprehensive income (loss)
Net of tax	1,395	1,452
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)	73	(151)
Actuarial (gains)	2,073	2,385
Total before tax	2,146	2,234
Tax expense or benefit	751	782
Net of tax	$ 1,395	$ 1,452