Inventories (Details) (USD $)	Mar. 28, 2014	Dec. 31, 2013
Inventory Disclosure [Abstract]
Aluminum and steel coil	$ 69,016,000	$ 58,153,000
Raw materials	16,592,000	15,291,000
Work in process	2,620,000	1,936,000
Finished products	16,501,000	14,380,000
Inventories, net	104,729,000	89,760,000
Inventory valuation reserves	$ (2,900,000)	$ (2,400,000)