Income tax expense (benefit) (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current:
Federal	$ 50,747	$ 17,121	$ 65,006
State	20,710	11,549	21,234
Foreign	0	0	151
Current income taxes	71,457	28,670	86,391
Deferred:
Federal	17,820	45,885	(3,735)
State	4,608	12,610	(625)
Investment tax credit - net	898	1,755	2,559
Deferred income taxes	23,326	60,250	(1,801)
Income taxes	$ 94,783	$ 88,920	$ 84,590