Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

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Derivative Financial Instruments (Details) (USD $)	3 Months Ended
Derivative Financial Instruments (Details) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Designated as hedging instrument
Gains or losses on derivative instruments, statement of income
Amount of gain (loss) recognized in income on related hedged items	$ 3,150,000	$ (1,504,000)
Futures \| Aluminum \| Long
Commodity contract commitments
Commodity contract (in MT/Lbs)	3,825
Futures \| Aluminum \| Short
Commodity contract commitments
Commodity contract (in MT/Lbs)	4,175
Futures \| Copper \| Long
Commodity contract commitments
Commodity contract (in MT/Lbs)	6,267
Futures \| Copper \| Short
Commodity contract commitments
Commodity contract (in MT/Lbs)	16,561
Futures \| Silver \| Short
Commodity contract commitments
Commodity contract (in MT/Lbs)	343
Commodity contract \| Futures
Fair values of derivative instruments, balance sheet
Commodity futures, asset derivatives (in dollars)	1,904,000		5,312,000
Commodity futures, liability derivatives (in dollars)	4,496,000		1,539,000
Commodity contract \| Futures \| Other current assets
Fair values of derivative instruments, balance sheet
Fair value of derivatives including required margin deposits	7,700,000		7,600,000
Commodity contract \| Futures \| Designated as hedging instrument
Gains or losses on derivative instruments, statement of income
Ineffectiveness - amount of gain recognized in income on related hedged items	107,000	296,000
Loss excluded from hedge effectiveness testing	1,300,000	183,000
Commodity contract \| Futures \| Designated as hedging instrument \| Cost of goods sold
Gains or losses on derivative instruments, statement of income
Amount of gain (loss) recognized in income on derivatives	(4,313,000)	1,617,000
Commodity contract \| Futures \| Designated as hedging instrument \| Other current assets
Fair values of derivative instruments, balance sheet
Commodity futures, asset derivatives (in dollars)	688,000		3,180,000
Commodity futures, liability derivatives (in dollars)	2,734,000		913,000
Commodity contract \| Futures \| Not designated as hedging instrument \| Cost of goods sold
Gains or losses on derivative instruments, statement of income
Amount of gain (loss) recognized in income on derivatives	6,996,000	7,956,000
Commodity contract \| Futures \| Not designated as hedging instrument \| Other current assets
Fair values of derivative instruments, balance sheet
Commodity futures, asset derivatives (in dollars)	1,216,000		2,132,000
Commodity futures, liability derivatives (in dollars)	1,762,000		626,000
Firm commitments \| Designated as hedging instrument \| Cost of goods sold
Gains or losses on derivative instruments, statement of income
Amount of gain (loss) recognized in income on related hedged items	494,000	984,000
Inventory \| Designated as hedging instrument \| Cost of goods sold
Gains or losses on derivative instruments, statement of income
Amount of gain (loss) recognized in income on related hedged items	$ 2,656,000	$ (2,488,000)