Environmental Settlement and Related Costs - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended	9 Months Ended	0 Months Ended
	Aug. 25, 2014	Sep. 30, 2014	Sep. 30, 2014	Oct. 01, 2014 Subsequent Event [Member] Charge
Environmental Exit Cost [Line Items]
Fines associated with the Consent Decree amount	$ 3,000,000	$ 6,600,000	$ 6,600,000
Preliminarily estimated cost of restoration	3,000,000
Maximum cost of restoration	9,000,000
Fine agreed to pay for violation of the Clean Water Act				$ 600,000
Period of probation				2 years
Number of misdemeanor charges to which the company pleaded guilty				3