Note 12 - Fair Value Measurements - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Investment available for sale	$ 16,200	$ 15,800
Fair Value, Recurring [Member]
Cash and cash equivalents	249,977	249,417
Restricted cash	20,471	23,785
Investment available for sale	16,151	15,772
Contingent payments	1,712	2,407
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	249,977	249,417
Restricted cash	20,471	23,785
Investment available for sale	0	0
Contingent payments	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents	0	0
Restricted cash	0	0
Investment available for sale	0	0
Contingent payments	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents	0	0
Restricted cash	0	0
Investment available for sale	16,151	15,772
Contingent payments	$ 1,712	$ 2,407