Rate Matters Rate Matters, NSP-Wisconsin (Details) - NSP-Wisconsin - Public Service Commission of Wisconsin (PSCW) [Member] - PSCW Proceeding - Tax Cuts and Jobs Act of 2017 [Member] $ in Millions	1 Months Ended
May 31, 2018 USD ($)
Public Utilities, General Disclosures [Line Items]
Tax Cuts and Jobs Act of 2017, Approved Refund of 2018 TCJA Benefits	$ 27
Tax Cuts and Jobs Act of 2017, Approved Deferral of 2018 TCJA Benefits	$ 5

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