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Note 6 - Equity - Summary of Restricted Awards Activity (Details)												3 Months Ended					9 Months Ended
	Sep. 15, 2023 USD ($) $ / shares	Jun. 21, 2023 USD ($) shares	Jun. 15, 2023 USD ($) $ / shares	Mar. 15, 2023 USD ($) $ / shares	Dec. 15, 2022 $ / shares	Dec. 08, 2022 $ / shares	Sep. 28, 2022 $ / shares	Sep. 15, 2022 USD ($) $ / shares	Jun. 15, 2022 USD ($) $ / shares	Mar. 15, 2022 $ / shares	Feb. 18, 2022 USD ($)	Sep. 30, 2023 USD ($) shares	Jun. 30, 2023 shares	Mar. 31, 2023 USD ($) $ / shares shares	Sep. 30, 2022 USD ($)	Jun. 30, 2022	Sep. 30, 2023 USD ($) shares	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Compensation costs \| $												$ 3,200,000			$ 2,000,000.0		$ 9,700,000	$ 6,200,000
Distribution ratio for outstanding award		0.2
Changes in fair value \| $		$ 0
Incremental compensation costs associated with modifications \| $		$ 0
Dividend declared \| $ / shares						$ 0.125	$ 0.11
Dividend accrued not paid \| $											$ 2,500,000			$ 354,000
Dividend payable \| $			$ 5,600,000	$ 5,600,000				$ 5,000,000.0	$ 5,000,000.0		$ 5,000,000.0	$ 733,000			$ 4,994,000		733,000	4,994,000	$ 5,500,000
Dividends paid \| $ / shares			$ 0.125	$ 0.125	$ 0.11			$ 0.11	$ 0.11	$ 0.11
Payment of dividends \| $																	$ 18,000,000.0	$ 15,000,000.0
Percentage dividend from financial performance of carbon												20	20			20
Class A Common Stock
Dividend payable \| $	$ 5,500,000
Dividends paid \| $ / shares	$ 0.125
Class B Common Stock
Number of shares issued		473,707
Dividends paid amount \| $	$ 1,500,000
Dividends paid \| $ / shares	$ 0.165
Percentage dividend from financial performance of carbon												20	20
Restricted Stock
Fair value of awards \| $														$ 2,500,000
Vesting period														3 years
Restricted Stock \| Class A Common Stock
Outstanding, shares (in shares)												1,900,000
Outstanding, shares (in shares)												1,800,000	1,900,000				1,800,000
Restricted Stock \| Class B Common Stock
Outstanding, shares (in shares)												400,000					400,000
Shares in restricted stock		680,718
Restricted Stock Units
Granted, shares (in shares)														518,348
Granted, Weighted average grant date fair value (in dollars per share) \| $ / shares														$ 10.61
Fair value of awards \| $														$ 5,500,000
Vesting period														3 years
Delivery Period														30 days
Shares delivered per unit awarded														1
Restricted Stock Units \| Class B Common Stock
Granted, shares (in shares)		136,819
Performance Stock Units
Vesting period														3 years
Delivery Period														30 days
Performance Stock Units \| Class B Common Stock
Granted, shares (in shares)		153,404
Employee Stock Option [Member] \| Class B Common Stock
Options granted		183,484
Executives and Employees \| Restricted Stock
Granted, shares (in shares)														296,115
Granted, Weighted average grant date fair value (in dollars per share) \| $ / shares														$ 10.61
Executives and Employees \| Performance Stock Units
Granted, shares (in shares)														518,348
Granted, Weighted average grant date fair value (in dollars per share) \| $ / shares														$ 18.09
Fair value of awards \| $														$ 9,400,000
Vesting period														3 years
Shares delivered per unit awarded														1
Executives and Employees \| Performance Stock Units \| Minimum
Potential earnings (as a percentage)														0.00%
Executives and Employees \| Performance Stock Units \| Maximum
Potential earnings (as a percentage)														200.00%
Executives and Employees \| Performance Stock Units Granted in 2022
Granted, shares (in shares)														248,706
Fair value of awards \| $																	$ 1,200,000
Directors \| Restricted Stock
Fair value of awards \| $														$ 600,000