Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Allowance for doubtful accounts	$ 3,963	$ 2,771
Allowance for doubtful accounts	$ 3,963	$ 2,771
Equity:
Common stock, shares authorized (in shares)	785,000,000
Common stock, shares issued	96,657,881	95,929,916
Common stock, shares outstanding	96,657,881	95,929,916
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ 191,760	$ 166,711
Class A Common
Equity:
Common stock, par value (in usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued	72,780,325	72,052,360
Common stock, shares outstanding	72,780,325	72,052,360
Class B Common
Equity:
Common stock, par value (in usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	275,000,000	275,000,000
Common stock, shares issued	23,877,556	23,877,556
Common stock, shares outstanding	23,877,556	23,877,556