Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Allowance for doubtful accounts	$ 6,491	$ 6,548
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	7,500,000	7,500,000
Preferred stock, shares issued
Preferred stock, shares outstanding
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	123,418,612	123,019,494
Common stock, shares outstanding	123,418,612	123,019,494