Commitments and Contingencies - Additional Information (Detail) (USD $)			1 Months Ended					1 Months Ended
	Jan. 31, 2013	Jan. 31, 2013 Effective date starting after January 31,2013	Oct. 17, 2012 Bojorquez	May 17, 2012 Bojorquez	Jul. 31, 2012 Augustus Claim	Feb. 08, 2012 Augustus	Jan. 31, 2013 Augustus	Jan. 14, 2013 Augustus Motion against others	Jul. 31, 2012 Augustus Motion against others
Loss Contingencies [Line Items]
Surety bonds	$ 311,600,000	$ 10,400,000
Total Letters of credit	104,200,000
Loss contingency amount accrued for probable losses	1,700,000
Amount of reasonably possible losses, Minimum	0
Amount of reasonably possible losses, Maximum	97,700,000
Loss Contingency, estimate of possible loss							94,200,000
Damages sought amount			4,800,000			103,100,000		4,500,000	12,400,000
Payment awarded to plaintiffs				$ 800,000	$ 89,700,000
Number of claim suit filed					3