Environmental Loss Contingency Disclosure - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Environmental Exit Cost [Line Items]
Total estimated clean up cost	$ 17,000,000
Accrual for estimated environmental remediation costs	13,500,000	13,900,000
Environmental liability, next 12 month	455,000
Environmental liability thereafter	13,000,000
Minimum
Environmental Exit Cost [Line Items]
Estimated environmental clean up costs	11,500,000
Maximum
Environmental Exit Cost [Line Items]
Estimated environmental clean up costs	$ 16,100,000