CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounts receivable, allowance for doubtful accounts	$ 4,240	$ 3,925
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, authorized	800	800
Preferred stock, issued
Preferred stock, outstanding
Common Stock
Common stock, par value	$ 0.001	$ 0.001
Common stock, authorized	1,500,000	1,500,000
Common stock, issued	141,357	139,836
Common stock, outstanding	108,296	111,129
Common Class B
Common stock, par value	$ 0.001	$ 0.001
Common stock, authorized	39,000	39,000
Common stock, issued
Common stock, outstanding