Note 7 - Share Repurchase Program (Details Textual) $ in Millions		3 Months Ended	6 Months Ended
	Jul. 07, 2017	Dec. 31, 2018 USD ($) shares	Jun. 30, 2019 USD ($) shares	Jun. 30, 2018 shares	Aug. 15, 2017 shares	Nov. 04, 2015 USD ($) shares	Dec. 31, 2007 shares
Stock Repurchase Program, Number of Shares Authorized to be Repurchased | shares			806,000		3,300,000	2,000,000	1,000,000
Stock Repurchase Program, Authorized Amount | $			$ 12.6			$ 40.0
Stock Repurchased and Retired During Period, Shares | shares		200,000	0	0
Stock Repurchased and Retired During Period, Value | $		$ 3.8
Stock Split from [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio	5
Stock Split To [Member]
Stockholders' Equity Note, Stock Split, Conversion Ratio	3