Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Statement of Financial Position [Abstract]
Allowances for doubtful accounts	$ 4,172	$ 3,404
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	95,000,000	95,000,000
Common stock, shares issued	53,623,637	55,389,636
Common stock, shares outstanding	44,943,069	46,709,068