Note 10 - Fair Value Measurement - Cash and Cash Equivalents (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Total assets	$ 74,237	$ 90,438	$ 75,864
Interest rate cash flow hedge, liabilities	5,564	1,098	1,500
Total liabilities	5,564	1,098
Fair Value, Inputs, Level 1 [Member]
Total assets	74,237	90,438	74,364
Interest rate cash flow hedge, liabilities	0	0	0
Total liabilities	0	0
Fair Value, Inputs, Level 2 [Member]
Total assets	0	0	1,500
Interest rate cash flow hedge, liabilities	5,564	1,098	1,500
Total liabilities	5,564	1,098
Fair Value, Inputs, Level 3 [Member]
Total assets	0	0	0
Interest rate cash flow hedge, liabilities	0	0	0
Total liabilities	0	0
Money Market Funds [Member]
Cash equivalents	68,579	84,613	68,765
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Cash equivalents	68,579	84,613	68,765
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	5,658	5,825	5,599
Restricted Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Other noncurrent assets	5,658	5,825	5,599
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