Derivative Instruments - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) Customer	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) Customer	Sep. 30, 2014 USD ($)
Derivative [Line Items]
Anticipated foreign-denominated sales hedge	$ 7,000,000		$ 7,000,000
Percentage of purchase commitments covering anticipated natural gas usage	30.00%		30.00%
Purchase commitment amount of anticipated natural gas usage	$ 1,533,000		$ 1,533,000
Number of subsidiaries purchased commitments for natural gas usage | Customer	1		1
Purchase commitments covering period anticipated usage, Description			Through March 2017 at one of its subsidiaries
Purchase of natural gas	$ 559,000	$ 543,000	$ 1,882,000	$ 1,645,000
Gains (losses) on foreign exchange transactions included in other income (expense)	18,000	$ (236,000)	(188,000)	$ (55,000)
Foreign Currency Sales Contract - Fair Value Hedges [Member]
Derivative [Line Items]
Fair value of assets held as collateral related to forward exchange contracts	$ 758,000		$ 758,000
Copper Purchases [Member]
Derivative [Line Items]
Percentage of anticipated purchases hedged	57.00%		57.00%
Time period for hedged purchases			9 months
Copper Purchases [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Anticipated purchases, hedged	$ 2,187,000		$ 2,187,000
Aluminum Purchases [Member]
Derivative [Line Items]
Percentage of anticipated purchases hedged	38.00%		38.00%
Time period for hedged purchases			6 months
Aluminum Purchases [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Anticipated purchases, hedged	$ 419,000		$ 419,000