Other Income, Expense and Non-Operating Other Income, net - Schedule of Other Income and Non-Operating Other Income, Net (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other income:
Realized and unrealized gains on carbon credits	$ 1,233	$ 876	$ 1,995
Settlements of litigation and potential litigation	545	2,303	1,562
Miscellaneous income	545	632	381
Total other income	2,323	3,811	3,938
Other expense:
Dismantle and demolition expense	2,578
Realized and unrealized losses on contractual obligations associated with carbon credits	1,233	721	1,844
Miscellaneous penalties	824	112	168
Losses on sales and disposals of property and equipment	737	996	1,280
Miscellaneous expense	302	289	531
Total other expense	5,674	2,118	3,823
Other income (expense), net	(3,351)	1,693	115
Non-operating other income, net:
Interest income	165	87	77
Miscellaneous income	1	263
Miscellaneous expense	(66)	(69)	(77)
Total non-operating other income, net	$ 100	$ 281