CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data	Sep. 30, 2011	Dec. 31, 2010
Trade accounts receivable, allowance for doubtful accounts	$ 4,082	$ 3,023
Convertible preferred stock, par value	$ 0.001	$ 0.001
Convertible preferred stock, shares authorized	1,000,000	1,000,000
Convertible preferred stock, shares outstanding	0	0
Common stock - Class A
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	30,000,000	30,000,000
Common stock, shares issued	2,757,110	2,863,912
Common stock, shares outstanding	2,757,110	2,863,912
Common stock - Class B
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	2,861,843	2,861,843
Common stock, shares outstanding	2,861,843	2,861,843
Common stock - Class C
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	3,121,048	3,121,048
Common stock, shares outstanding	3,121,048	3,121,048
Common stock - Class D
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	42,185,133	45,541,082
Common stock, shares outstanding	42,185,133	45,541,082