Note 1 - Organization and Significant Accounting Policies (Details Textual) - USD ($) $ / shares in Units, $ in Thousands							2 Months Ended	4 Months Ended	6 Months Ended	10 Months Ended	12 Months Ended			14 Months Ended
	Mar. 05, 2021	Mar. 03, 2021	Mar. 02, 2021	Jan. 25, 2021	Jan. 21, 2021	Jan. 20, 2021	Feb. 24, 2023	Oct. 28, 2021	Aug. 01, 2020	Jun. 01, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2022	Aug. 30, 2022
Stock Issued During Period, Shares, New Issues (in shares)											3,885,048,000	20,165,635,000
Stock Issued During Period, Value, New Issues											$ 40,580	$ 514,059	$ 71,050
Proceeds from Issuance of Common Stock											$ 40,580	$ 514,059	$ 71,050
Common Stock, Par or Stated Value Per Share (in dollars per share)											$ 0.01	$ 0.01		$ 0.01	$ 0.01
January 2020 Equity Distribution Agreement [Member]
Equity Agreement, Maximum Number of Shares Issuable (in shares)									200,000,000
Stock Issued During Period, Shares, New Issues (in shares)									634,145
Stock Issued During Period, Value, New Issues									$ 19,800
Proceeds from Issuance of Common Stock									$ 19,400
August 2020 Equity Distribution Agreement [Member]
Equity Agreement, Maximum Number of Shares Issuable (in shares)										150,000,000
Stock Issued During Period, Shares, New Issues (in shares)										5,498,730
Stock Issued During Period, Value, New Issues										$ 150,000
Proceeds from Issuance of Common Stock										$ 147,400
January 2021 Underwriting Agreement [Member]
Stock Issued During Period, Shares, New Issues (in shares)				1,748,000	228,000	1,520,000
Proceeds from Issuance of Common Stock				$ 45,200
Shares Issued, Price Per Share (in dollars per share)						$ 26.00
March 2021 Underwriting Agreement [Member]
Stock Issued During Period, Shares, New Issues (in shares)	1,840,000	240,000	1,600,000
Proceeds from Issuance of Common Stock	$ 50,000
Shares Issued, Price Per Share (in dollars per share)			$ 27.25
June 2021 Equity Distribution Agreement [Member]
Equity Agreement, Maximum Number of Shares Issuable (in shares)								250,000,000
Stock Issued During Period, Shares, New Issues (in shares)								9,881,467
Stock Issued During Period, Value, New Issues								$ 250,000
Proceeds from Issuance of Common Stock								$ 246,000
October 2021 Equity Distribution Agreement [Member]
Equity Agreement, Maximum Number of Shares Issuable (in shares)														250,000,000
Stock Issued During Period, Shares, New Issues (in shares)														7,052,188
Stock Issued During Period, Value, New Issues														$ 119,600
Proceeds from Issuance of Common Stock														$ 117,600
October 2021 Equity Distribution Agreement [Member] | Subsequent Event [Member]
Stock Issued During Period, Shares, New Issues (in shares)							2,690,000
Stock Issued During Period, Value, New Issues							$ 32,200
Proceeds from Issuance of Common Stock							$ 31,700