Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Accumulated Other Comprehensive Income (Loss)	Mar. 31, 2012 Accumulated Other Comprehensive Income (Loss)	Mar. 31, 2013 Post retirement medical plan Accumulated Other Comprehensive Income (Loss)	Mar. 31, 2012 Post retirement medical plan Accumulated Other Comprehensive Income (Loss)	Mar. 31, 2012 Decker defined benefit pension Accumulated Other Comprehensive Income (Loss)	Mar. 31, 2013 Decker defined benefit pension Accumulated Other Comprehensive Income (Loss)	Dec. 31, 2012 Decker defined benefit pension Accumulated Other Comprehensive Income (Loss)
Other Comprehensive Income (Loss) (AOCI) by component, net of tax
Balance at the beginning of the period	$ (20,158)	$ (20,461)	$ (20,461)	$ (18,614)	$ (14,684)	$ (12,707)	$ (5,907)	$ (5,777)	$ (5,777)
Other comprehensive income before reclassifications			19	58	19		58
Amounts reclassified from accumulated other comprehensive income			284	252	284	252
Net current period other comprehensive income			303	310	303	252	58
Balance at the end of the period	$ (20,158)	$ (20,461)	$ (20,158)	$ (18,304)	$ (14,381)	$ (12,455)	$ (5,849)	$ (5,777)	$ (5,777)