Other Expense, Income and Non-Operating Other Expense (Income), Net - Schedule of Other Income and Non-Operating Other Income, Net (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Other expense:
Realized and unrealized losses on contractual obligations associated with carbon credits	$ 1,634	$ 233
Losses on sales and disposals of property and equipment	844	50
Dismantle and demolition expense		1,188
Miscellaneous penalties		312
Impairment on long-lived assets		210
Miscellaneous expense	105	37
Total other expense	2,583	2,030
Other income:
Realized and unrealized gains on carbon credits	1,925	233
Settlements of litigation and potential litigation		545
Miscellaneous income	149	184
Total other income	2,074	962
Other expense, net	509	1,068
Non-operating other expense (income), net:
Interest income	(95)	(8)
Miscellaneous expense	18	24
Total non-operating other expense (income), net	$ (77)	$ 16