Note 2 - Significant Accounting Policies - Recast Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total revenues	$ 217,364	$ 164,456	$ 127,210
Operating loss	(13,597)	(15,694)	(19,074)
Income taxes	(2,459)	(1,131)	(686)
Net loss	(13,694)	(17,710)	$ (21,283)
Current assets:
Prepaid expenses and other current assets	7,130	3,650
Current liabilities:
Accrued expenses and other short term liabilities	42,453	28,479
Deferred revenues	73,891	58,478
Long-term liabilities:
Deferred revenues	7,034	3,562
Restatement Adjustment [Member] | Accounting Standards Update 2014-09 [Member]
Total revenues	(1,974)	1,407
Operating loss	178	3,699
Income taxes	(328)	(182)
Net loss	(151)	3,517
Current assets:
Prepaid expenses and other current assets	9,865
Current liabilities:
Accrued expenses and other short term liabilities	1,014
Deferred revenues	(227)
Long-term liabilities:
Deferred revenues	130
Pro Forma [Member] | Accounting Standards Update 2014-09 [Member]
Total revenues	215,390	165,863
Operating loss	(13,419)	(11,995)
Income taxes	(2,787)	(1,313)
Net loss	(13,845)	$ (14,193)
Current assets:
Prepaid expenses and other current assets	16,995
Current liabilities:
Accrued expenses and other short term liabilities	43,467
Deferred revenues	73,664
Long-term liabilities:
Deferred revenues	$ 7,164