Note 5 - Details of Selected Balance Sheet Accounts - Accounts Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounts receivable, net:
Accounts receivable	$ 77,089	$ 68,161
Allowance for doubtful accounts	(1,300)	(1,338)
Total accounts receivable, net	75,789	66,823
Trade Accounts Receivable [Member]
Accounts receivable, net:
Accounts receivable	54,190	46,692
Unbilled Revenue [Member]
Accounts receivable, net:
Accounts receivable	22,741	20,555
Other Receivable [Member]
Accounts receivable, net:
Accounts receivable	$ 158	$ 914