Condensed Consolidated Balance Sheet (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Dec. 31, 2010
Trade receivables, allowance for doubtful accounts	$ 7,625	$ 9,391
Property, accumulated depreciation	$ 322,520	$ 316,288
Percentage of cumulative preferred stock	4.50%	4.50%
Common stock, authorized	180,000,000	180,000,000
Common stock, par value	$ 0	$ 0
Common stock, issued	62,081,391	62,081,391
Common stock, shares outstanding	36,643,634	36,519,726
Stock compensation trust, shares	1,215,769	1,360,714
Preferred Stock, 4 1/ 2% Cumulative [Member]
Preferred stock, par value	$ 50	$ 50
Preferred stock, authorized	100,000	100,000
Preferred stock, callable per share	$ 52.50	$ 52.50
Preferred stock, issued	71,373	71,373
Treasury shares, shares	52,878	52,878
Second Cumulative Preferred Voting Stock [Member]
Preferred stock, par value	$ 10	$ 10
Preferred stock, authorized	1,000,000	1,000,000
Preferred stock, issued	0	0
Common Stock [Member]
Treasury shares, shares	24,221,988	24,200,951