Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014 acre	Mar. 12, 2014
Commitments And Contingencies Disclosure [Abstract]
Accrued liability for legal contingencies	$ 12,000,000
Environmental tax and royalty obligations		100,000,000
Retain right of obligations	67,500,000
Cost for restoration of plaintiffs property	200,000,000
Area of land	825
Undiscounted reserve for environmental remediation	$ 92,000,000