Note 9 - Fair Value Measurement - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Total assets	$ 62,743	$ 71,995	$ 80,493
Interest rate swap	5,001	7,606	8,353
Total liabilities	5,001	7,606	8,353
Fair Value, Inputs, Level 1 [Member]
Total assets	62,743	71,995	80,493
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	5,001	7,606	8,353
Total liabilities	5,001	7,606	8,353
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	61,231	70,483	78,981
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Cash equivalents	61,231	70,483	78,981
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	1,512	1,512	1,512
Restricted Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Other noncurrent assets	1,512	1,512	1,512
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