Transactions with Affiliated Companies (Details) (USD $)	0 Months Ended	12 Months Ended
	Sep. 15, 2009 acre sqft	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Transactions with affiliated entities
Sales		$ 282,817,000	$ 278,786,000	$ 239,954,000
Accounts receivable		42,864,000	42,893,000
Purchase price paid for land, building and equipment		223,525,000	167,007,000	133,394,000
Heidtman Steel Products (Heidtman)
Transactions with affiliated entities
Sales		244,531,000	242,300,000	202,897,000
Percentage of consolidated net sales		3.00%	3.00%	3.00%
Accounts receivable		38,093,000	35,646,000	31,544,000
Purchases		11,372,000	18,998,000	18,275,000
Accounts payable		800,000	882,000	969,000
Area of land (in acres)	32
Area of building (in square foot)	387,000
Repurchase option		27,900,000
Lease term	5 years
Monthly rental expense for real estate and equipment		289,000
Heidtman Steel Products (Heidtman) | Land and Building
Transactions with affiliated entities
Purchase price paid for land, building and equipment	9,300,000
Heidtman Steel Products (Heidtman) | Equipment
Transactions with affiliated entities
Purchase price paid for land, building and equipment	18,600,000
Other smaller affiliated entities
Transactions with affiliated entities
Sales		38,286,000	36,486,000	37,057,000
Accounts receivable		4,771,000	7,247,000	6,577,000
Purchases		238,114,000	239,395,000	177,166,000
Accounts payable		$ 14,344,000	$ 5,702,000	$ 12,601,000