Note 10 - Fair Value Measurement - Cash and Cash Equivalents (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Total assets	$ 63,574	$ 100,531	$ 41,984
Interest rate swap	8,890	4,603	2,530
Total liabilities	8,890	4,603	2,530
Fair Value, Inputs, Level 1 [Member]
Total assets	63,574	100,531	41,984
Interest rate swap	0	0	0
Total liabilities	0	0	0
Fair Value, Inputs, Level 2 [Member]
Total assets	0	0	0
Interest rate swap	8,890	4,603	2,530
Total liabilities	8,890	4,603	2,530
Fair Value, Inputs, Level 3 [Member]
Total assets	0	0	0
Interest rate swap	0	0	0
Total liabilities	0	0	0
Money Market Funds [Member]
Cash equivalents	58,693	94,696	36,159
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Cash equivalents	58,693	94,696	36,159
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Cash equivalents	0	0	0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Cash equivalents	0	0	0
Restricted Cash [Member]
Other noncurrent assets	4,881	5,835	5,825
Restricted Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Other noncurrent assets	4,881	5,835	5,825
Restricted Cash [Member] | Fair Value, Inputs, Level 2 [Member]
Other noncurrent assets	0	0	0
Restricted Cash [Member] | Fair Value, Inputs, Level 3 [Member]
Other noncurrent assets	$ 0	$ 0	$ 0