Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Trade receivables, allowance for doubtful accounts	$ 3,985	$ 4,396
Prepaid expenses and other current assets	4,960	4,245
Intangible assets subject to amortization, net	21,714	22,349
Accounts payable and accrued expenses	29,855	39,158
Long-term debt, less current maturities, bond discount	2,848	2,982
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	55,090,121	54,404,226
Common stock, shares outstanding	55,090,121	54,404,226
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	7,064	4,916
Prepaid expenses and other current assets	274	274
Intangible assets subject to amortization, net	20,299	20,880
Accounts payable and accrued expenses	$ 3,756	$ 3,576