Other Expense, Income and Non-Operating Other Expense (Income), Net - Schedule of Other Income and Non-Operating Other Expense (Income), Net (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Other expense:
Realized and unrealized losses on contractual obligations associated with carbon credits		$ 313	$ 1,634	$ 546
Losses on sales and disposals of property and equipment	164	(50)	1,008
Dismantle and demolition expense	559	912	559	2,100
Miscellaneous penalties	3	484	3	796
Impairment on long-lived assets				210
Miscellaneous expense	18	67	123	104
Total other expense	744	1,726	3,327	3,756
Other income:
Realized and unrealized gains on carbon credits		313	1,925	546
Settlements of litigation and potential litigation				545
Miscellaneous income	140	270	289	454
Total other income	140	583	2,214	1,545
Other expense, net	604	1,143	1,113	2,211
Non-operating other expense (income), net:
Interest income	(79)	(4)	(174)	(12)
Miscellaneous income
Miscellaneous expense	3	12	21	36
Total non-operating other expense (income), net	$ (76)	$ 8	$ (153)	$ 24