Note Q - Stockholders' Equity (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		4 Months Ended	12 Months Ended
	Oct. 24, 2019	Mar. 31, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Feb. 28, 2020	Oct. 17, 2016
Common Stock, Shares Authorized (in shares)			45,000,000	45,000,000
Preferred Stock, Shares Authorized (in shares)			5,000,000	5,000,000
Proceeds from Issuance of Common Stock			$ 39,203	$ 0	$ 0
Stock Offering, Maximum Value, New Issues	$ 250,000
Second ATM Offering [Member]
Common Stock, Maximum Amount to be Sold							$ 250,000
Stock Issued During Period, Shares, New Issues (in shares)		1,600,000
Shares Issued, Price Per Share (in dollars 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
Third ATM Offering [Member] | Raymond James & Associates, Inc. [Member]
Common Stock, Maximum Amount to be Sold						$ 55,000
Stock Issued During Period, Shares, New Issues (in shares)			4,500,000
Shares Issued, Price Per Share (in dollars per share)			$ 9.00
Proceeds from Issuance of Common Stock			$ 39,400