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Regulatory Matters - Schedule of Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Regulated Asset Liability [Line Items]
Earning a return, asset	$ 482
Not earning a return, asset	486
Pending regulatory treatment, asset	16
Regulatory assets	137	$ 146
Non-current regulatory assets	847	894
Earning a return, liability	856
Not earning a return, liability	71
Pending Regulatory Treatment Liability	15
Regulatory liabilities	108	76
Non-current regulatory liabilities	834	857
Deferred natural gas costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	25
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	25	9
Non-current regulatory liabilities	0	0
Deferred Power Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	14
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	8	0
Non-current regulatory liabilities	6	4
Utility Plant Retirement Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	448
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	0	0
Non-current regulatory liabilities	448	417
Excess Deferred Income Taxes [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	293
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	14	15
Non-current regulatory liabilities	279	293
Other Income Tax Related Liabilities [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	0
Not earning a return, liability	64
Pending Regulatory Treatment Liability	0
Regulatory liabilities	5	25
Non-current regulatory liabilities	59	57
Climate Commitment Act [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	50
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	50	0
Non-current regulatory liabilities	0	46
Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	19
Not earning a return, liability	0
Pending Regulatory Treatment Liability	5
Regulatory liabilities	0	0
Non-current regulatory liabilities	$ 24	24
Decoupling Rebates [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory liability	1 year
Earning a return, liability	$ 4
Not earning a return, liability	0
Pending Regulatory Treatment Liability	0
Regulatory liabilities	4	19
Non-current regulatory liabilities	0	6
COVID-19 Deferrals [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	0
Not earning a return, liability	0
Pending Regulatory Treatment Liability	10
Regulatory liabilities	0	0
Non-current regulatory liabilities	10	10
Other Regulatory Liabilities [Member]
Regulated Asset Liability [Line Items]
Earning a return, liability	9
Not earning a return, liability	7
Pending Regulatory Treatment Liability	0
Regulatory liabilities	8	8
Non-current regulatory liabilities	8	9
Deferred Income Tax [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	246
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	246	244
Pension and Other Postretirement Benefit Plans [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets			12 years
Earning a return, asset	0
Not earning a return, asset	106
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	106	118
Climate Commitment Act [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	44
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	44	0
Non-current regulatory assets	0	37
Energy Commodity Derivatives [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	41
Pending regulatory treatment, asset	0
Regulatory assets	27	51
Non-current regulatory assets	14	18
Unamortized Debt Repurchase Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	5
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	$ 5	6
Settlement with Coeur d'Alene Tribe [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	35 years
Earning a return, asset	$ 36
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	36	37
Demand Side Management Programs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	38
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	$ 38	10
Decoupling Surcharge [Member]
Regulated Asset Liability [Line Items]
Remaining amortization period, regulatory assets	1 year
Earning a return, asset	$ 24
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	12	5
Non-current regulatory assets	12	5
Utility Plant Abandoned [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	39
Not earning a return, asset	3
Pending regulatory treatment, asset	0
Regulatory assets	4	0
Non-current regulatory assets	38	38
Interest Rate Swaps [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	172
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	172	179
Deferred power costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	36
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	9	29
Non-current regulatory assets	27	21
Deferred Natural Gas Costs [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	61
Non-current regulatory assets	0	0
AFUDC Above FERC Allowed Rate [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	49
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	49	50
COVID-19 Deferrals [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	0
Not earning a return, asset	0
Pending regulatory treatment, asset	12
Regulatory assets	0	0
Non-current regulatory assets	12	12
Advanced Meter Infrastructure [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	26
Not earning a return, asset	0
Pending regulatory treatment, asset	0
Regulatory assets	0	0
Non-current regulatory assets	26	29
Other Regulatory Assets [Member]
Regulated Asset Liability [Line Items]
Earning a return, asset	45
Not earning a return, asset	52
Pending regulatory treatment, asset	4
Regulatory assets	35	0
Non-current regulatory assets	$ 66	$ 81

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