CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts	$ 2,979	$ 2,144
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	250,000,000
Common Stock, Shares, Issued	59,182,176	3,802,972
Common Stock, Shares, Outstanding	59,182,176	3,802,972
Class A-1 Common Stock
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	0	40,000,000
Common Stock, Shares, Issued	0	16,100,000
Common Stock, Shares, Outstanding	0	16,100,000
Class A-2 Common Stock
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	40,000,000	0
Common Stock, Shares, Issued	6,731,845	0
Common Stock, Shares, Outstanding	6,731,845	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	40,331,989	38,462,541
Common Stock, Shares, Outstanding	40,331,989	38,462,541