Other Expense, Other Income and Non-Operating Other Income (Expense), net (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Other expense:
Losses on sales and disposals of property and equipment	$ 116	$ 101	$ 667	$ 996
Loss on contractual obligations associated with carbon credits	248		248	936
Miscellaneous expense	20	48	191	600
Total other expense	384	149	1,106	2,532
Other income:
Gains on carbon credits	248	(2)	248	1,028
Settlements of litigation and potential litigation				757
Miscellaneous income	241	60	589	250
Total other income	489	58	837	2,035
Non-operating other income (expense), net:
Interest income	22	20	70	61
Miscellaneous income			263
Miscellaneous expense	(24)	(22)	(63)	(58)
Total non-operating other income (expense), net	$ (2)	$ (2)	$ 270	$ 3