Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	$ 87,150
Change in accumulated other comprehensive income before reclassifications	15,644	9,418
Reclassification adjustments from accumulated other comprehensive income	(464)	4
Balance at end of period	102,330
Net unrealized appreciation on investments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	116,601
Change in accumulated other comprehensive income before reclassifications	15,644
Reclassification adjustments from accumulated other comprehensive income	(963)
Balance at end of period	131,282
Liability for underfunded employee benefit costs [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(29,451)
Change in accumulated other comprehensive income before reclassifications	0
Reclassification adjustments from accumulated other comprehensive income	499
Balance at end of period	$ (28,952)