Investment in Knife River (Details 3) - USD ($) $ in Thousands, shares in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	May 31, 2023
Fair value, balance sheet grouping [Line Items]
Retained Shares Ownership Percentage				10.00%
Retained Shares				5.7
Unrealized Gain (Loss) on Investments		$ 3,501	$ (12,357)
Investment in Knife River
Fair value, balance sheet grouping [Line Items]
Investments, Fair Value Disclosure	$ 276,200	276,200
Unrealized Gain (Loss) on Investments	$ 30,200	$ 170,200