Utility Plant (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Public Utility, Property, Plant and Equipment
Accumulated amortization of capital leases	$ 2,600	$ 1,600
Utility Plant
Distribution plant	7,488,629	7,028,731
Production plant	3,147,987	3,096,092
Transmission plant	1,556,666	1,494,781
General plant	746,758	697,501
Intangible plant (including capitalized software)1	797,691	779,767
Plant acquisition adjustment	242,826	242,826
Underground storage	43,391	39,498
Liquefied natural gas storage	12,628	12,628
Plant held for future use	46,020	45,929
Recoverable Cushion Gas	8,655	8,655
Plant not classified	316,933	384,794
Finance leases, net of accumulated amortization2	105,020	881
Less: accumulated provision for depreciation	(4,031,458)	(3,671,094)
Subtotal	10,481,746	10,160,989
Construction work in progress	870,204	712,204
Net utility plant	$ 11,351,950	10,873,193
Minimum
Public Utility, Property, Plant and Equipment
Distribution plant, Estimated Useful Life	20 years
Production plant, Estimated Useful Life	12 years
Transmission plant, Estimated Useful Life	43 years
General plant, Estimated Useful Life	5 years
Public Utilities, Property, Plant and Equipment, Intangible, Estimated Useful Life 1	3 years
Underground storage, Estimated Useful Life	25 years
Liquefied natural gas storage, Estimated Useful Life	25 years
Minimum | Franchise Rights [Member]
Public Utility, Property, Plant and Equipment
General plant, Estimated Useful Life	10 years
Minimum | Software and Software Development Costs [Member]
Public Utility, Property, Plant and Equipment
General plant, Estimated Useful Life	3 years
Maximum
Public Utility, Property, Plant and Equipment
Distribution plant, Estimated Useful Life	65 years
Production plant, Estimated Useful Life	90 years
Transmission plant, Estimated Useful Life	75 years
General plant, Estimated Useful Life	75 years
Public Utilities, Property, Plant and Equipment, Intangible, Estimated Useful Life 1	50 years
Underground storage, Estimated Useful Life	60 years
Liquefied natural gas storage, Estimated Useful Life	60 years
Maximum | Franchise Rights [Member]
Public Utility, Property, Plant and Equipment
General plant, Estimated Useful Life	50 years
Maximum | Software and Software Development Costs [Member]
Public Utility, Property, Plant and Equipment
General plant, Estimated Useful Life	10 years
Subsidiaries [Member]
Utility Plant
Distribution plant	$ 9,026,042	8,592,720
Production plant	3,815,599	3,767,014
Transmission plant	1,663,559	1,601,731
General plant	773,662	726,327
Intangible plant (including capitalized software)1	788,240	770,317
Plant acquisition adjustment	282,792	282,792
Underground storage	56,820	52,927
Liquefied natural gas storage	14,498	14,498
Plant held for future use	46,172	46,081
Recoverable Cushion Gas	8,655	8,655
Plant not classified	316,933	384,794
Finance leases, net of accumulated amortization2	105,020	881
Less: accumulated provision for depreciation	(6,416,246)	(6,087,748)
Subtotal	10,481,746	10,160,989
Construction work in progress	870,204	712,204
Net utility plant	$ 11,351,950	$ 10,873,193