Note 3 - Share-based Compensation - Nonvested Award Activity (Details) - Stock Unit Award [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		9 Months Ended
		Sep. 30, 2018	Dec. 31, 2017
Outstanding & Unvested at beginning of period (in shares)		33
Outstanding & Unvested at beginning of period, weighted average price per share (in dollars per share)	[1]	$ 16.08
Outstanding & Unvested at beginning of period, weighted average fair value	[1]	$ 343	$ 516
Granted (in shares)		6
Granted, weighted average price per share (in dollars per share)	[1]	$ 21.04
Granted, weighted average fair value	[1]	$ 126
Converted to common stock (in shares)		(15)
Cancelled (in shares)		(5)
Forfeited (in shares)
Outstanding & Unvested at end of period (in shares)		19
Outstanding & Unvested at end of period, weighted average price per share (in dollars per share)	[1]	$ 18.20

[1] Weighted average price per share is the weighted grant price based on the closing market price of each of the stock grants related to each grant of stock unit awards. The weighted average fair value is the weighted average share price times the number of shares.