Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2011
Current assets:
Allowance for doubtful accounts	$ 22,230	$ 21,491
Accumulated depreciation on property, plant and equipment	$ 789,786	$ 784,864
Shareholders' equity:
Common shares, par value	$ 1.25	$ 1.25
Common shares, shares authorized	120,000,000	120,000,000
Common shares, shares issued	58,931,000	58,931,000
Treasury shares, shares	11,537,000	10,796,000