Note 7 - Segment Reporting (Details Textual) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019
Number of Reportable Segments	2
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 475,915	$ 470,353
Adjusted EBITDA	$ 86,025	$ 87,128
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | UNITED STATES
Concentration Risk, Percentage	77.00%	72.00%
Geographic Concentration Risk [Member] | Net Assets, Geographic Area [Member] | UNITED STATES
Concentration Risk, Percentage	82.00%		80.00%
Amounts Adjusted from the Domestic Segment to the International Segment [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total		$ 2,750
Adjusted EBITDA		$ (253)