Condensed Consolidated Balance Sheets Parenthetical (USD $) In Thousands, except Per Share data	Sep. 30, 2011	Dec. 31, 2010
Current assets
Allowance for doubtful accounts	$ 1,745	$ 1,347
Other assets
Accumulated depreciation on property and equipment	30,969	26,375
Accumulated amortization on intangible assets	$ 23,959	$ 20,656
Stockholders' equity
Preferred stock, shares authorized	50,000	50,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common Stock Class A
Stockholders' equity
Common Stock, Par Value	$ 0.01	$ 0.01
Common Stock, shares authorized	100,000	100,000
Common Stock, shares issued	30,546	30,166
Common Stock, shares outstanding	30,546	30,166
Common Stock Class B
Stockholders' equity
Common Stock, Par Value	$ 0.0001	$ 0.0001
Common Stock, shares authorized	50,000	50,000
Common Stock, shares issued	10,811	11,151
Common Stock, shares outstanding	10,811	11,151