Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Trade receivables, related parties	$ 4,253	$ 4,653
Trade receivables, allowance for doubtful accounts	3,131	2,566
Prepaid expenses and other current assets	13,217	6,260
Property and equipment, accumulated depreciation	185,229	179,869
Accumulated amortization of Intangible assets	92,194	87,632
Intangible assets subject to amortization, net	24,196	26,758
Accounts payable and accrued expenses	52,795	57,563
Unamortized debt issuance costs	3,386	3,761
Related Parties
Prepaid expenses and other current assets	274	274
Intangible assets subject to amortization, net	8,633	9,555
Accounts payable and accrued expenses	$ 2,392	$ 2,548
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	64,576,497	66,069,325
Common stock, shares outstanding	64,576,497	66,069,325
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	14,927,613	14,927,613
Common stock, shares outstanding	14,927,613	14,927,613
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