Note 6 - Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Nov. 07, 2019	Dec. 31, 2020	Dec. 31, 2019	Feb. 28, 2018	Jul. 31, 2015
Stock Repurchase Program, Authorized Amount					$ 25,000
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
Dividends Payable, Amount Per Share (in dollars per share)	$ 1.00
Dividends, Total	$ 20,700		$ 20,679