Commitments and Contingencies - Additional Information (Detail) (USD $)			1 Months Ended			1 Months Ended
	Apr. 30, 2013	Apr. 30, 2013 Effective date starting after April 30, 2013	Jul. 31, 2012 Augustus Claim	Feb. 08, 2012 Augustus	Apr. 30, 2013 Augustus	Jan. 14, 2013 Augustus Motion against others	Jul. 31, 2012 Augustus Motion against others	Apr. 11, 2013 Bojorquez	May 17, 2012 Bojorquez
Loss Contingencies [Line Items]
Surety bonds	$ 345,700,000	$ 85,300,000
Total letters of credit	104,000,000
Loss contingency amount accrued for probable losses	1,400,000
Amount of reasonably possible losses, Minimum	0
Amount of reasonably possible losses, Maximum	96,400,000
Loss Contingency, estimate of possible loss					94,200,000
Damages sought amount				103,100,000		4,500,000	12,400,000	2,500,000
Payment awarded to plaintiffs			$ 89,700,000						$ 800,000
Number of claim suit filed			3