Investment in Knife River (Details 3) - USD ($) $ in Thousands, shares in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Jun. 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	$ 140,000	$ 4,885	$ (10,579)
Investment in Knife River
Fair value, balance sheet grouping [Line Items]
Investments, Fair Value Disclosure	$ 246,100	246,100
Unrealized Gain (Loss) on Investments		$ 140,000