Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts	$ 8,617	$ 7,291
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	50,424,800	50,605,440
Common stock, shares outstanding	50,424,800	50,605,440