Fair Value of Financial Assets and Liabilities (Tables)

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis by Hierarchy Level

Recurring Fair Value Measurements — As of March 31, 2021, there were no derivative assets measured at fair value on a recurring basis. At Dec. 31, 2020, NSP-Wisconsin's derivative assets measured at fair value on a recurring basis were as follows:

	Dec. 31, 2020
	Fair Value						Fair Value Total		Netting (a)		Total (b)
(Millions of Dollars)	Level 1		Level 2		Level 3
Current derivative assets
Natural gas commodity	$	—	$	1	$	—	$	1	$	—	$	1

(a)    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 March 31, 2021 and Dec. 31, 2020. The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.

(b)    Included in prepayments and other current assets balance of $5 million at March 31, 2021 and $7 million at Dec. 31, 2020 on the consolidated balance sheets.

Carrying Amount and Fair Value of Long-term Debt

Other financial instruments for which the carrying amount did not equal fair value:

	March 31, 2021				Dec. 31, 2020
(Millions of Dollars)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Long-term debt, including current portion	$	907	$	1,042	$	906	$	1,124