Note 9 - Fair Value Measurements - Discounted Cash Flow Assumptions (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Time-to-liquidity (months) (Month)	2 years	2 years
Minimum [Member]
Discount rate	40.00%	4.30%
Maximum [Member]
Discount rate	9.00%	9.30%