Recurring Fair Value Measurements (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Derivative liability		$ 46		$ 46		$ 42
Derivative Liability, Noncurrent		81		81		102
Obligation to return cash		0		0		0
Right to reclaim cash		6		6
Commodity Trading
Changes in Level 3 Commodity Derivatives [Roll Forward]
Balance at beginning of period		117	$ 230	107	$ 56
Settlements	[1]	(32)	(88)	(60)	(180)
Gains recognized in earnings (b)	[2]	17	15	15	106
Net (losses) gains recognized as regulatory assets and liabilities (a)	[1]	(33)	35	(91)	53
Balance at end of period		69	$ 192	69	192
Purchases (a)	[1]			98	$ 157
Fair Value Measured on a Recurring Basis
Derivatives, Fair Value [Line Items]
Derivative asset, gross		119		119		149
Netting, asset	[3]	(53)		(53)		(60)
Derivative Asset, Noncurrent		58		58		68
Derivative liability, gross		84		84		93
Netting, liability	[3]	(53)		(53)		(65)
Derivative liability		31		31		28
Derivative Liability, Noncurrent		57		57		74
Changes in Level 3 Commodity Derivatives [Roll Forward]
Derivative Asset, Current		66		66		89
Fair Value Measured on a Recurring Basis | Level 1
Derivatives, Fair Value [Line Items]
Derivative asset, gross		5		5		15
Derivative liability, gross		8		8		23
Fair Value Measured on a Recurring Basis | Level 2
Derivatives, Fair Value [Line Items]
Derivative asset, gross		41		41		43
Derivative liability, gross		65		65		62
Fair Value Measured on a Recurring Basis | Level 3
Derivatives, Fair Value [Line Items]
Derivative asset, gross		73		73		91
Derivative liability, gross		11		11		8
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative asset, gross		79		79		86
Netting, asset	[3]	(49)		(49)		(58)
Derivative Asset, Noncurrent		58		58		68
Derivative liability, gross		80		80		89
Netting, liability	[3]	(49)		(49)		(63)
Derivative liability		31		31		26
Derivative Liability, Noncurrent		57		57		74
Changes in Level 3 Commodity Derivatives [Roll Forward]
Derivative Asset, Current		30		30		28
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Electric Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		36		36		58
Netting, asset	[3]	(4)		(4)		(2)
Derivative liability, gross		4		4		2
Netting, liability	[3]	(4)		(4)		(2)
Derivative liability		0		0		0
Changes in Level 3 Commodity Derivatives [Roll Forward]
Derivative Asset, Current		32		32		56
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		4		4		5
Netting, asset	[3]	0		0		0
Derivative liability, gross		0		0		2
Netting, liability	[3]	0		0		0
Derivative liability		0		0		2
Changes in Level 3 Commodity Derivatives [Roll Forward]
Derivative Asset, Current		4		4		5
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Level 1 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative asset, gross		5		5		15
Derivative liability, gross		8		8		23
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Level 1 | Electric Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		0		0		0
Derivative liability, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Level 1 | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		0		0		0
Derivative liability, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Level 2 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative asset, gross		37		37		38
Derivative liability, gross		65		65		60
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Level 2 | Electric Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		0		0		0
Derivative liability, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Level 2 | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		4		4		5
Derivative liability, gross		0		0		2
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Level 3 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative asset, gross		37		37		33
Derivative liability, gross		7		7		6
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Level 3 | Electric Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		36		36		58
Derivative liability, gross		4		4		2
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Level 3 | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative asset, gross		0		0		0
Derivative liability, gross		0		0		0
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets
Derivatives, Fair Value [Line Items]
Derivative asset, gross		93		93		127
Netting, asset	[3]	(35)		(35)		(59)
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 1
Derivatives, Fair Value [Line Items]
Derivative asset, gross		11		11		21
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 2
Derivatives, Fair Value [Line Items]
Derivative asset, gross		33		33		40
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Level 3
Derivatives, Fair Value [Line Items]
Derivative asset, gross		49		49		66
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative asset, gross		93		93		127
Netting, asset	[3]	(35)		(35)		(59)
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Other Derivative Instruments | Level 1 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative asset, gross		11		11		21
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Other Derivative Instruments | Level 2 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative asset, gross		33		33		40
Fair Value Measured on a Recurring Basis | Other Noncurrent Assets | Other Derivative Instruments | Level 3 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative asset, gross		49		49		66
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative liability, gross		97		97		134
Netting, liability	[3]	(40)		(40)		(60)
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 1
Derivatives, Fair Value [Line Items]
Derivative liability, gross		18		18		37
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 2
Derivatives, Fair Value [Line Items]
Derivative liability, gross		37		37		55
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Level 3
Derivatives, Fair Value [Line Items]
Derivative liability, gross		42		42		42
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Other Derivative Instruments | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative liability, gross		97		97		134
Netting, liability	[3]	(40)		(40)		(60)
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Other Derivative Instruments | Level 1 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative liability, gross		18		18		37
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Other Derivative Instruments | Level 2 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative liability, gross		37		37		55
Fair Value Measured on a Recurring Basis | Other Noncurrent Liabilities | Other Derivative Instruments | Level 3 | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative liability, gross		42		42		42
Fair Value, Measurements, Nonrecurring | PPAs
Derivatives, Fair Value [Line Items]
Derivative liability	[4]	15		15		14
Derivative Liability, Noncurrent	[4]	$ 24		$ 24		$ 28

[1] Relates primarily to FTR instruments administered by MISO.

[2] Relates to commodity trading and is subject to substantial offsetting losses and gains on derivative instruments categorized as levels 1 and 2 in the consolidated income statement. See above tables for the income statement impact of derivative activity, including commodity trading gains and losses.

[3] NSP-Minnesota nets derivative instruments and related collateral on its consolidated balance sheets when supported by a legally enforceable master netting agreement. At Sept. 30, 2023 and Dec. 31, 2022, derivative assets and liabilities include no obligations to return cash collateral. At both Sept. 30, 2023 and Dec. 31, 2022 derivative assets and liabilities include rights to reclaim cash collateral of $5 million and $6 million, respectively. Counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.

[4] NSP-Minnesota currently applies the normal purchase exception to qualifying PPAs. Balance relates to specific contracts that were previously recognized at fair value prior to applying the normal purchase exception, and are being amortized over the remaining contract lives along with the offsetting regulatory assets and liabilities.