CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts	$ 3,341	$ 2,979
Common Stock, Shares, Issued	40,331,989	40,331,989
Common Stock, Shares, Outstanding	40,331,989	40,331,989
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	66,258,163	59,182,176
Common Stock, Shares, Outstanding	66,258,163	59,182,176
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	6,731,845
Common Stock, Shares, Outstanding	0	6,731,845
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
Common Stock, Shares, Outstanding	40,331,989