Contingencies - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Site Contingency [Line Items]
Environmental and legal losses	$ 25,800,000	$ 25,800,000
Cash outlays related to legal and environmental matters	$ 400,000	$ 300,000
Contribution for future response costs	5.00%
Payment of environmental response costs	$ 2,500,000
Minimum [Member]
Site Contingency [Line Items]
Environmental and legal losses	25,600,000
Maximum [Member]
Site Contingency [Line Items]
Environmental and legal losses	$ 46,300,000