Note 1 - Organization and Significant Accounting Policies (Details Textual) - USD ($) $ / shares in Units, $ in Thousands										3 Months Ended	4 Months Ended	10 Months Ended		12 Months Ended					14 Months Ended
		Mar. 07, 2023	Oct. 29, 2021	Mar. 05, 2021	Mar. 03, 2021	Mar. 02, 2021	Jan. 25, 2021	Jan. 21, 2021	Jan. 20, 2021	Dec. 31, 2022	Oct. 28, 2021	Dec. 31, 2023	Jun. 01, 2021	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021	Dec. 31, 2022	Aug. 30, 2022
Stock Issued During Period, Shares, New Issues (in shares)	[1]									3,885,048				15,880,039		3,885,048
Stock Issued During Period, Value, New Issues										$ 40,580				$ 159,438	[2]	$ 40,580	[2]	$ 514,059
Proceeds from Issuance of Common Stock														159,438		40,580		514,059
Direct Operating Costs														$ 715		$ 831		1,090
Common Stock, Par or Stated Value Per Share (in dollars per share)										$ 0.01		$ 0.01		$ 0.01		$ 0.01			$ 0.01	$ 0.01
Reclassification to Conform To Current Period [Member]
Direct Operating Costs																$ 3,300		$ 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
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)			9,742,188
Stock Issued During Period, Value, New Issues			$ 151,800
Proceeds from Issuance of Common Stock			$ 149,300
March 2023 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)												13,190,039
Stock Issued During Period, Value, New Issues												$ 129,900
Proceeds from Issuance of Common Stock												$ 127,800

[1] As of December 31, 2023, the Company had entered into eleven equity distribution agreements, ten of which have either been terminated because all shares were sold or were replaced with a subsequent agreement.

[2] Net proceeds are net of the underwriters' discount, if applicable, and other offering costs.