Fair Value of Financial Assets and Liabilities - Interest Rate Derivatives (Details) - USD ($) $ in Millions		Jun. 30, 2022		Dec. 31, 2021
Interest Rate Swap
Derivative [Line Items]
Derivative Liability, Notional Amount		$ 0		$ 0
Natural Gas Commodity | Other Derivative Instruments | Other Current Assets | Fair Value, Recurring [Member]
Derivative [Line Items]
Derivative Asset, Gross		1		1
Netting	[1]	0		0
Derivative Asset, Net	[3]	1	[2]	1
Natural Gas Commodity | Other Derivative Instruments | Other Current Assets | Level 1 | Fair Value, Recurring [Member]
Derivative [Line Items]
Derivative Asset, Gross		0		0
Natural Gas Commodity | Other Derivative Instruments | Other Current Assets | Level 2 | Fair Value, Recurring [Member]
Derivative [Line Items]
Derivative Asset, Gross		1		1
Natural Gas Commodity | Other Derivative Instruments | Other Current Assets | Level 3 | Fair Value, Recurring [Member]
Derivative [Line Items]
Derivative Asset, Gross		$ 0		$ 0

[1] NSP-Wisconsin nets derivative instruments and related collateral on its consolidated balance sheets when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at June 30, 2022 and Dec. 31, 2021. The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.

[2] Included in other current liabilities at June 30, 2022 and Dec. 31, 2021 on the consolidated balance sheets.

[3] Included in prepayments and other current assets at June 30, 2022 and Dec. 31, 2021 on the consolidated balance sheets.