Fair Value of Financial Assets and Liabilities (Tables)

9 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

Gross Notional Amounts of Commodity Forwards and Options

Gross notional amounts of commodity options:

(Amounts in Millions) (a)(b)	Sept. 30, 2019	Dec. 31, 2018
Million British thermal Units (MMBtu) of natural gas	0.6	1.2

^(a)  Amounts are not reflective of net positions in the underlying commodities.

^(b) 

Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise.

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

Recurring Fair Value Measurements — The following tables presents for each of the fair value hierarchy levels, NSP-Wisconsin's derivative assets and liabilities measured at fair value on a recurring basis:

	Sept. 30, 2019
	Fair Value						Fair Value Total		Netting (a)		Total (b)
(Millions of Dollars)	Level 1		Level 2		Level 3
Current derivative assets
Natural gas commodity	$	—	$	0.8	$	—	$	0.8	$	—	$	0.8
Current derivative liabilities
Natural gas commodity	$	—	$	0.4	$	—	$	0.4	$	—	$	0.4

	Dec. 31, 2018
	Fair Value						Fair Value Total		Netting (a)		Total (c)
(Millions of Dollars)	Level 1		Level 2		Level 3
Current derivative assets
Natural gas commodity	$	—	$	0.2	$	—	$	0.2	$	—	$	0.2

^(a)  NSP-Wisconsin nets derivative instruments and related collateral in its consolidated balance sheet when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at Sept. 30, 2019 and Dec. 31, 2018.  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 $4.6 million and other current liabilities balance of $15.0 million at Sept. 30, 2019, in the consolidated balance sheets.

^(c) 

Included in prepayments and other current assets balance of $3.3 million at Dec. 31, 2018, in 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:

	Sept. 30, 2019				Dec. 31, 2018
(Millions of Dollars)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Long-term debt, including current portion	$	807.9	$	954.0	$	807.5	$	850.4