Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Condensed Consolidated Balance Sheets
Allowance for doubtful accounts receivable	$ 2,497	$ 3,402
Accumulated depreciation on property, plant and equipment	233,597	231,167
Accumulated amortization on other intangible assets	9,651	9,541
Deferred income taxes included in other long-term liabilities	$ 58,587	$ 53,935
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	119,063,456	118,737,456
Treasury stock, shares (in shares)	56,532,637	56,348,026