Inventories (Details Textual) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2012	Dec. 31, 2011
Inventories (Textual) [Abstract]
Probable increase in inventory cost, if current cost had been used to value inventories		$ 12	$ 29
Inventories accounted under the LIFO method		86.00%	88.00%
Effect of decreased cost of materials sold	$ 5.8