Sources and Tax Effects of Differences Between Benefit from Income Taxes and Amount Computed by Applying Federal Statutory Income Tax Rate to Losses from Continuing Operations before Income Taxe (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Effective Tax Rates Line Items
Income tax benefit at the federal statutory tax rate of 35%	$ (42,146)	$ (53,809)	$ (67,272)
Provision for (Benefit from) Income Tax Differences
Statutory depletion	(19,608)	(18,931)	(20,301)
State and local income taxes, net of federal income tax benefit	(2,076)	(6,445)	3,465
Fair market value over tax basis of charitable contributions	(2,007)	0	(3,223)
Undistributed foreign earnings	0	(2,553)	(3,331)
Prior year true up adjustments	(657)	3,115	(1,095)
Other, net	2	140	2,094
Total benefit from income taxes	$ (66,492)	$ (78,483)	$ (89,663)
Income tax benefit at the federal statutory tax rate of 35%	35.00%	35.00%	35.00%
Provision for (Benefit from) Income Tax Differences
Statutory depletion	16.30%	12.30%	10.60%
State and local income taxes, net of federal income tax benefit	1.70%	4.20%	(1.80%)
Fair market value over tax basis of charitable contributions	1.70%	0.00%	1.70%
Undistributed foreign earnings	0.00%	1.70%	1.70%
Prior year true up adjustments	0.50%	(2.10%)	0.60%
Other, net	0.00%	(0.10%)	(1.20%)
Total income tax benefit	55.20%	51.00%	46.60%