Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 7,843,783	$ 7,317,269
Less accumulated depreciation	1,880,265	1,787,550
Net property, plant and equipment	$ 5,657,480	5,247,232
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Property, plant, and equipment, net
Electric Plant
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Equipment	$ 5,205,788	4,848,349
Natural Gas Plant
Property, Plant and Equipment [Line Items]
Public Utilities, Property, Plant and Equipment, Equipment	1,371,045	1,252,229
Plant Acquisition adjustment [Member]
Property, Plant and Equipment [Line Items]
Plant acquisition adjustment(2)	686,328	686,328
Common Plant
Property, Plant and Equipment [Line Items]
Common and Other Plant	268,970	235,746
Construction work in progress
Property, Plant and Equipment [Line Items]
Construction work in process	311,652	294,617
Computer Software, Intangible Asset
Property, Plant and Equipment [Line Items]
Less accumulated amortization	(306,038)	(282,487)
Property, Plant and Equipment [Member]
Property, Plant and Equipment [Line Items]
Finance Lease, Right-of-Use Asset, after Accumulated Amortization	7,200	9,200
Basin Capital Lease [Member]
Property, Plant and Equipment [Line Items]
Finance Lease, Right-of-Use Asset, after Accumulated Amortization	$ 7,000	$ 9,000