Income Taxes - Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current:
Federal	$ 50,180	$ 21,337	$ 11,737
State	13,707	7,176	4,414
Foreign	0	0	0
Current income taxes	63,887	28,513	16,151
Deferred:
Federal	(5,960)	16,105	19,092
State	(601)	4,245	6,546
Investment tax credit - net	2,147	898	1,755
Deferred income taxes	(4,414)	21,248	27,393
Income taxes	$ 59,473	$ 49,761	$ 43,544