Summary of Significant Accounting Policies, Textuals (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounting policies additional disclosures
Advertising costs	$ 400,000	$ 400,000	$ 300,000
Research and development costs	6,400,000	6,100,000	4,900,000
Net non-cash LIFO (benefit) charges	(4,900,000)	(7,100,000)	16,500,000
Excess of current cost over the stated LIFO value of inventory	24,500,000	29,400,000
Effect of LIFO Inventory Liquidation on Income	22,300,000
Impairment of the carrying value of goodwill	0	0
Discount rate used in estimating liabilities for worker compensation claims	0.75%	1.00%
Undiscounted workers' compensation liabilities	27,300,000	24,300,000
Margin deposits with counterparties	0	0
Margin deposits from counterparties	0	0
Performance shares
Accounting policies additional disclosures
Performance award vesting period, years	3 years
Fabricated Products
Accounting policies additional disclosures
Net non-cash LIFO (benefit) charges	$ (4,900,000)	$ (7,100,000)	$ 16,500,000
Maximum
Accounting policies additional disclosures
Number of days to maturity for commerial paper classified as cash and cash equivalents	90 days
Period over which accounts receivable is due, days	60 days
Minimum
Accounting policies additional disclosures
Period over which accounts receivable is due, days	30 days
Number of days in maturity for commerial paper classified as short-term investments	90 days