Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheet [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 23,112	$ 20,357
Common Stock, par value	$ 0.01	$ 0.01
Common Stock, shares authorized	120,000,000	120,000,000
Common Stock, shares issued	72,740,302	70,752,670
Common Stock, shares outstanding	72,740,302	70,752,670
Preferred Stock, par value	$ 0.01	$ 0.01
Preferred Stock, shares authorized	1,000,000	1,000,000
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Treasury Stock, shares	246,037	246,037