Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Trade receivables, allowance for doubtful accounts	$ 3,342	$ 4,396
Prepaid expenses and other current assets	5,434	4,245
Intangible assets subject to amortization, net	20,446	22,349
Accounts payable and accrued expenses	29,025	39,158
Long-term debt, less current maturities, bond discount	0	2,982
Class A common stock [Member]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	260,000,000	260,000,000
Common stock, shares issued	59,257,790	54,404,226
Common stock, shares outstanding	59,257,790	54,404,226
Class B common stock [Member]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	19,430,035	22,188,161
Common stock, shares outstanding	19,430,035	22,188,161
Class U common stock [Member]
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 [Member]
Trade receivables, related parties	6,555	4,916
Prepaid expenses and other current assets	274	274
Intangible assets subject to amortization, net	19,139	20,880
Accounts payable and accrued expenses	$ 4,004	$ 3,576