Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Other Comprehensive Income (Loss) (AOCI) by component, net of tax
Beginning balance, January 1	$ (11,299)
Ending balance, March 31	(10,905)
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)		316
Net current period other comprehensive income (loss)		316
Ending balance, March 31		(9,963)
Post retirement medical plan | Accumulated Other Comprehensive Income (Loss)
Other Comprehensive Income (Loss) (AOCI) by component, net of tax
Beginning balance, January 1	(11,299)	(6,517)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	394	316
Net current period other comprehensive income (loss)	394	316
Ending balance, March 31	$ (10,905)	(6,201)
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)