Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Comprehensive Income (Loss) (AOCI) by component, net of tax
Balance at the beginning of the period	$ (11,299)	$ (10,279)	$ (20,461)
Other comprehensive income (loss) before reclassifications	(2,441)	(3,691)	9,031
Amounts reclassified from accumulated other comprehensive income (loss)	789	2,671	1,151
Net current period other comprehensive income (loss)	(1,652)	(1,020)	10,182
Balance at the end of the period	(12,951)	(11,299)	(10,279)
Post retirement medical plan
Other Comprehensive Income (Loss) (AOCI) by component, net of tax
Balance at the beginning of the period	(11,299)	(8,242)	(16,409)
Other comprehensive income (loss) before reclassifications	(2,441)	(3,691)	7,017
Amounts reclassified from accumulated other comprehensive income (loss)	789	633	1,151
Net current period other comprehensive income (loss)	(1,652)	(3,058)	8,168
Balance at the end of the period	(12,951)	(11,299)	(8,242)
Decker defined benefit pension
Other Comprehensive Income (Loss) (AOCI) by component, net of tax
Balance at the beginning of the period	0	(2,038)	(4,052)
Other comprehensive income (loss) before reclassifications	0	0	2,014
Amounts reclassified from accumulated other comprehensive income (loss)	0	2,038	0
Net current period other comprehensive income (loss)	0	2,038	2,014
Balance at the end of the period	$ 0	$ 0	$ (2,038)