Fair Value of Financial Assets and Liabilities - Recurring Fair Value Measurements (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Prepayments and other		$ 8	$ 11
Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Pre-tax fair value gains (losses) recognized during the period in regulatory (assets) and liabilities		1
Derivative, Gain (Loss) on Derivative, Net		2
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Net		0	2	[1]
Derivative Liability		$ 0	1	[1]
Derivative Liability, Not Subject to Master Netting Arrangement	[1]		1
Derivative Liability, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	[1],[2]		0
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Natural Gas Commodity | Level 1
Derivatives, Fair Value [Line Items]
Derivative Liability, Not Subject to Master Netting Arrangement	[1]		0
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Natural Gas Commodity | Level 2
Derivatives, Fair Value [Line Items]
Derivative Liability, Not Subject to Master Netting Arrangement	[1]		1
Fair Value Measured on a Recurring Basis | Other Derivative Instruments | Natural Gas Commodity | Level 3
Derivatives, Fair Value [Line Items]
Derivative Liability, Not Subject to Master Netting Arrangement	[1]		0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross	[1]		2
Netting	[1],[2]		0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity | Level 1
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross	[1]		0
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity | Level 2
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross	[1]		2
Fair Value Measured on a Recurring Basis | Other Current Assets | Other Derivative Instruments | Natural Gas Commodity | Level 3
Derivatives, Fair Value [Line Items]
Derivative Asset, Gross	[1]		0
Fair Value Measured on a Recurring Basis | Other Current Liabilities | Other Derivative Instruments | Natural Gas Commodity
Derivatives, Fair Value [Line Items]
Derivative Liability			$ 1

[1] $2 million included in prepayments and other current assets and $1 million included in other current liabilities at Dec. 31, 2022 on the consolidated balance sheet.

[2] NSP-Wisconsin nets derivative instruments and related collateral on its consolidated balance sheets when supported by a legally enforceable master netting agreement. Counterparty netting excludes settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.