Note 10 - Equity (Details Textual) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Feb. 28, 2019	Jul. 31, 2015
Stock Repurchase Program, Authorized Amount				$ 25
Treasury Stock, Shares, Acquired (in shares)	0	0
Sale of Stock, Individual Ownership, Percent, Maximum			4.99%
Preferred Stock Purchase Right to be Exchanged for Common Stock Above Maximum Ownership Threshold (in shares)			1