Income tax Effective Income Tax Rate Reconcilitation (Details)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Tax Disclosure [Abstract]
Federal statutory tax rate	21.00%	21.00%
Federal tax credits	(16.20%)	(9.30%)
State and local taxes, net of federal tax benefit	9.10%	9.00%
Flow through depreciation and cost basis differences	0.20%	1.00%
Excess deferred tax amortization	(3.30%)	(3.70%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	(0.10%)	(2.10%)
Effective tax rate	10.70%	15.90%