Summary of Significant Accounting Policies (Details 7) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Components of comprehensive income
Net income	$ 34,287	$ 23,599	$ 25,995	$ 27,012	$ 31,826	$ 32,266	$ 13,103	$ 26,671	$ 32,913	$ 23,637	$ (11,851)	$ 25,807	$ 110,893		$ 103,866	$ 70,506
Change in net unrealized gains and losses on fixed maturities and equity securities
Net unrealized holding gains and losses on fixed maturities and equity securities arising during the period													(375,184)		204,460	281,202
Less: reclassification adjustment for net gains included in income before income tax													22,245		27,298	37,663
Total, before tax													(397,429)		177,162	243,539
Income tax expense (benefit)													(149,019)		62,984	86,585
Total, net of tax													(248,410)	[1],[2]	114,178	156,954
Change in net funded status of pension and other postretirement benefit obligations
Before tax													5,645		1,276	(4,801)
Income tax expense (benefit)													2,110		345	(1,714)
Total, net of tax													3,535		931	(3,087)
Total													$ (133,982)		$ 218,975	$ 224,373

[1] All amounts are net of tax.

[2] The $22,245 pretax amount reclassified from accumulated other comprehensive income is included in net realized investment gains and losses and the $7,786 related tax expense (benefit) is included in income tax expense in the Consolidated Statement of Operations for the year ended December 31, 2013.