Cash flow information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Supplemental Cash Flow Information [Abstract]
Interest, net*	$ 15,657,000	$ 14,303,000
Income taxes paid (refunded), net	(363,000)	13,880,000
AFUDC borrowed	586,000	348,000
Right-of-use assets obtained in exchange for new operating lease liabilities	10,175,000	9,236,000	$ 55,987,000
Property, plant and equipment additions in accounts payable	25,730,000	20,594,000	57,605,000
Debt assumed in connection with a business combination	$ 0	$ 0	$ 10,000