Consolidated Balance Sheets (Parenthetical) (USD $)	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Consolidated Balance Sheets
Common stock, par value per share	$ 0.1	$ 0.1	$ 0.1
Common stock, shares authorized	80,000,000	80,000,000	80,000,000
Common stock, shares issued	30,235,164	30,235,164	30,235,164
Treasury shares at cost	942,722	685,315	881,003