Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data	Jun. 30, 2011	Dec. 31, 2010
Condensed Consolidated Balance Sheets
Allowance for doubtful accounts, accounts receivable	$ 567	$ 586
Property, plant and equipment, accumulated depreciation	$ 315,601	$ 302,944
Preferred shares, par value	$ 0.10	$ 0.10
Preferred shares, shares authorized	5,000	5,000
Preferred shares, issued	0	0
Common shares, par value	$ 0.10	$ 0.10
Common shares, shares authorized	145,000	145,000
Common shares, issued	60,054	61,196
Common shares, outstanding	59,943	61,085
Treasury shares, shares	111	111