CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 5,392	$ 5,329
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Authorized	50,000,000	50,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Class A Common Stock
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	350,000,000	350,000,000
Common Stock, Shares, Issued	86,321,013	78,956,555
Common Stock, Shares, Outstanding	86,321,013	78,956,555
Class A-2 Common Stock
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	40,000,000	40,000,000
Common Stock, Shares, Issued	0	0
Common Stock, Shares, Outstanding	0	0
Class B Common Stock
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	150,000,000	150,000,000
Common Stock, Shares, Issued	18,461,975	26,026,843
Common Stock, Shares, Outstanding	18,461,975	26,026,843