Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Condensed Consolidated Balance Sheets [Abstract]
Receivables, allowance for doubtful accounts	$ 5,683	$ 5,860
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares issued	0	0
Common stock, shares authorized	150,000,000	150,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares issued	86,949,111	85,968,630
Treasury stock, shares	3,024,599	2,734,747