FAIR VALUE MEASUREMENTS (Tables)

9 Months Ended

Sep. 30, 2021

Fair Value Disclosures [Abstract]

Schedule of fair value of assets and liabilities measured on a recurring basis categorized by level within the fair value hierarchy

The following tables summarize our financial assets and liabilities that were accounted for at fair value on a recurring basis, categorized by level within the fair value hierarchy:

	September 30, 2021
(in millions)	Level 1		Level 2		Level 3		Total
Derivative assets
Natural gas contracts	$	37.6	$	2.1	$	—	$	39.7
FTRs	—		—		2.1		2.1
Coal contracts	—		15.4		—		15.4
Total derivative assets	$	37.6	$	17.5	$	2.1	$	57.2
Derivative liabilities
Natural gas contracts	$	—	$	0.4	$	—	$	0.4

	December 31, 2020
(in millions)	Level 1		Level 2		Level 3		Total
Derivative assets
Natural gas contracts	$	1.6	$	0.1	$	—	$	1.7
FTRs	—		—		1.2		1.2
Coal contracts	—		0.4		—		0.4
Total derivative assets	$	1.6	$	0.5	$	1.2	$	3.3
Derivative liabilities
Natural gas contracts	$	1.6	$	0.3	$	—	$	1.9
Coal contracts	—		0.5		—		0.5
Total derivative liabilities	$	1.6	$	0.8	$	—	$	2.4

Reconciliation of changes in the fair value of items categorized as level 3 measurements

The following table summarizes the changes to derivatives classified as Level 3 in the fair value hierarchy:

	Three Months Ended September 30				Nine Months Ended September 30
(in millions)	2021		2020		2021		2020
Balance at the beginning of the period	$	2.8	$	3.4	$	1.2	$	1.3
Purchases	—		—		3.1		4.0
Settlements	(0.7)		(1.5)		(2.2)		(3.4)
Balance at the end of the period	$	2.1	$	1.9	$	2.1	$	1.9

Schedule of carrying value and fair value of financial instruments not recorded at fair value

The following table shows the financial instruments included on our balance sheets that were not recorded at fair value:

	September 30, 2021				December 31, 2020
(in millions)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Long-term debt, including current portion (1)	$	1,614.5	$	1,858.0	$	1,613.5	$	1,935.9

(1)The carrying amount of long-term debt excludes finance lease obligations of $33.9 million and $31.3 million at September 30, 2021 and December 31, 2020, respectively.