Note 3 - Accounts Receivable and Allowance - Activity in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Balance--beginning of period	$ 10,772	$ 11,464
Provision	11,509	21,583
Charge-offs	(11,005)	(22,383)
Recoveries		108
Balance--end of period	$ 11,276	$ 10,772