Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Trade receivables, allowance for doubtful accounts	$ 3,100	$ 3,199
Trade receivables, related parties	10,882	7,102
Prepaid expenses and other current assets	5,295	4,087
Property and equipment, accumulated depreciation	193,532	184,084
Accumulated amortization of Intangible assets	74,697	71,678
Intangible assets subject to amortization, net	20,193	19,812
Accounts payable and accrued expenses	32,195	31,246
Related Parties
Prepaid expenses and other current assets	274	274
Intangible assets subject to amortization, net	16,239	18,559
Accounts payable and accrued expenses	$ 3,695	$ 3,994
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	58,893,970	59,793,603
Common stock, shares outstanding	58,893,970	59,793,603
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	18,930,035	18,969,222
Common stock, shares outstanding	18,930,035	18,969,222
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