Note Q - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		4 Months Ended	12 Months Ended
	Jan. 10, 2020	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 17, 2016
Common Stock, Shares Authorized			45,000,000	45,000,000
Preferred Stock, Shares Authorized			5,000,000	5,000,000
Stock Issued During Period, Value, New Issues					$ 21,572
Proceeds from Issuance of Common Stock			$ 0	$ 0	$ 21,572
Subsequent Event [Member]
Stock Offering, Maximum Value, New Issues	$ 250,000
Stock Issued During Period, Shares, New Issues	0
Second ATM Offering [Member]
Common Stock, Maximum Amount to be Sold						$ 250,000
Stock Issued During Period, Value, New Issues		$ 1,600
Shares Issued, Price Per Share		$ 31.55
Proceeds from Issuance of Common Stock		$ 48,800
Second ATM Offering [Member] | Raymond James & Associates, Inc. [Member]
Common Stock, Maximum Amount to be Sold						$ 50,000