Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Trade receivables, allowance for doubtful accounts	$ 2,566	$ 2,550
Trade receivables, related parties	4,653	7,357
Prepaid expenses and other current assets	6,260	4,870
Property and equipment, accumulated depreciation	179,869	204,343
Accumulated amortization of Intangible assets	87,632	81,770
Intangible assets subject to amortization, net	26,758	13,120
Accounts payable and accrued expenses	59,522	30,810
Unamortized debt issuance costs	3,761	2,365
Related Parties
Prepaid expenses and other current assets	274	274
Intangible assets subject to amortization, net	9,555	11,598
Accounts payable and accrued expenses	$ 2,548	$ 3,886
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	66,069,325	65,886,256
Common stock, shares outstanding	66,069,325	65,886,256
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