Note 8 - Capital Stock (Details Textual) - USD ($)			2 Months Ended		12 Months Ended												113 Months Ended	144 Months Ended
	Feb. 12, 2025	Jan. 08, 2025	Feb. 27, 2025	[1]	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2024	Dec. 31, 2024	Feb. 21, 2025	Feb. 14, 2025	Oct. 12, 2022	Dec. 09, 2021	Feb. 08, 2018	Jul. 29, 2015
Common Stock, Shares Authorized (in shares)					100,000,000	100,000,000											100,000,000	100,000,000
Common Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.01	$ 0.01											$ 0.01	$ 0.01
Preferred Stock, Shares Authorized (in shares)					20,000,000	20,000,000											20,000,000	20,000,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.01	$ 0.01											$ 0.01	$ 0.01
Stock Repurchased and Retired During Period, Value					$ 3,290,000	$ 9,424,000	$ 24,610,000
Common Stock, Dividends, Per Share, Declared (in dollars per share)					$ 1.44	$ 1.8	$ 2.475	$ 3.9	$ 3.95	$ 4.8	$ 5.35	$ 8.4	$ 8.4	$ 9.6	$ 10.8	$ 6.975		$ 68.13
Share Repurchase Program [Member]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased (in shares)																								400,000
Stock Repurchase Program, Additional Shares Authorized (in shares)																					4,300,000	3,372,399	904,564
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased (in shares)																					6,183,601	3,539,861	1,061,315	156,751
Stock Repurchased and Retired During Period, Shares (in shares)					396,241	1,072,789											5,144,602
Stock Repurchased and Retired During Period, Value					$ 3,300,000	$ 9,400,000											$ 77,500,000
Shares Acquired, Average Cost Per Share (in dollars per share)					$ 8.3	$ 8.79											$ 15.07
Subsequent Event [Member]
Total Number Of Shares Authorized (in shares)																				220,000,000
Common Stock, Shares Authorized (in shares)																				200,000,000
Common Stock, Par or Stated Value Per Share (in dollars per share)																				$ 0.01
Preferred Stock, Shares Authorized (in shares)																				20,000,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)																				$ 0.01
Aggregate Par Value of Authorized Shares																				$ 2,200,000
Common Stock, Dividends, Per Share, Declared (in dollars per share)	$ 0.12	$ 0.12	$ 0.24
Subsequent Event [Member] | Share Repurchase Program [Member]
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased (in shares)																			3,832,361

[1] On January 8, 2025, the Company declared a dividend of $0.12 per share to be paid on February 27, 2025. On February 12, 2025, the Company declared a dividend of $0.12 per share to be paid on March 28, 2025. The effect of these dividends are included in the table above, but are not reflected in the Company’s financial statements as of December 31, 2024.