Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2015	Dec. 31, 2014
Other Comprehensive Income (Loss) (AOCI) by component, net of tax
Beginning balance, January 1			$ (11,299)
Ending balance, March 31		(11,102)	(11,299)
Accumulated Other Comprehensive Income (Loss)
Other Comprehensive Income (Loss) (AOCI) by component, net of tax
Beginning balance, January 1	(10,279)
Other comprehensive income (loss) before reclassifications	0
Amounts reclassified from accumulated other comprehensive income (loss)	158
Net current period other comprehensive income (loss)	158
Ending balance, March 31	(10,121)
Post retirement medical plan | Accumulated Other Comprehensive Income (Loss)
Other Comprehensive Income (Loss) (AOCI) by component, net of tax
Beginning balance, January 1	(6,517)	(11,299)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	158	197
Net current period other comprehensive income (loss)	158	197
Ending balance, March 31	(6,359)	(11,102)
Decker defined benefit pension | Accumulated Other Comprehensive Income (Loss)
Other Comprehensive Income (Loss) (AOCI) by component, net of tax
Beginning balance, January 1	(3,763)
Other comprehensive income (loss) before reclassifications	0
Amounts reclassified from accumulated other comprehensive income (loss)	0
Net current period other comprehensive income (loss)	0
Ending balance, March 31	$ (3,763)