Income tax Effective Income Tax Rate Reconcilitation (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Federal statutory tax rate	21.00%	21.00%	21.00%	21.00%
Federal tax credits	(9.20%)	(11.20%)	(9.70%)	(10.10%)
State and local taxes, net of federal tax benefit	8.00%	8.90%	8.70%	8.70%
Flow through depreciation and cost basis differences	1.60%	(1.50%)	0.90%	(1.00%)
Excess deferred tax amortization	(4.20%)	(4.60%)	(4.30%)	(3.70%)
Other	0.00%	0.00%	0.00%	(4.20%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	(0.10%)	(3.50%)	(0.10%)	(1.50%)
Effective tax rate	17.10%	9.10%	16.50%	9.20%