(6) Other Long-Term Assets and Other Income (Detail) - Other Long-Term Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Other income:
MSHA reimbursements*	$ 2,053	[1]	$ 2,336	[1]
Miscellaneous	408		126
	$ 2,461		$ 2,462

[1] See "MSHA Reimbursements" below.