Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Trade receivables, allowance for doubtful accounts	$ 4,396	$ 3,926
Prepaid expenses and other current assets	4,245	5,939
Intangible assets subject to amortization	22,349	24,598
Accounts payable and accrued expenses	39,158	39,750
Long-term debt, less current maturities, bond discount	2,982	4,134
Class A Common Stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	260,000,000	260,000,000
Common stock, shares issued	54,404,226	53,514,769
Common stock, shares outstanding	54,404,226	53,514,769
Class B Common Stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	22,188,161	22,188,161
Common stock, shares outstanding	22,188,161	22,188,161
Class U Common stock
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	9,352,729	9,352,729
Common stock, shares outstanding	9,352,729	9,352,729
Related Parties
Trade receivables, related parties	4,916	5,608
Prepaid expenses and other current assets	274	274
Intangible assets subject to amortization	20,880	23,513
Accounts payable and accrued expenses	$ 3,576	$ 5,691