Derivatives and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value, by Balance Sheet Grouping

The fair value of derivatives reflected in the accompanying consolidated balance sheets are set forth in the table below.

	December 31, 2020				December 31, 2019
	Asset Derivative		Liability Derivative		Asset Derivative		Liability Derivative
	(Dollars in millions)
Foreign currency option contracts	$	10.3	$	—	$	1.1	$	—
Coal contracts related to forecasted sales	0.9		(8.8)		20.1		(0.1)
Coal trading contracts	23.4		(23.1)		81.1		(74.2)
Total derivatives	34.6		(31.9)		102.3		(74.3)
Effect of counterparty netting	(30.2)		30.2		(74.3)		74.3
Variation margin posted (held)	6.5		—		(22.1)		—
Net derivatives and margin as classified in the balance sheets	$	10.9	$	(1.7)	$	5.9	$	—

Derivative Instruments, Gain (Loss)

The tables below show the amounts of pre-tax gains and losses related to the Company’s derivatives.

	Year Ended December 31, 2020
	Total gain (loss) recognized in income		Gain realized in income on derivatives		Unrealized gain (loss) recognized in income on derivatives
Financial Instrument
	(Dollars in millions)
Foreign currency option contracts	$	12.9	$	5.8	$	7.1
Coal contracts related to forecasted sales	(23.8)		5.8		(29.6)
Coal trading contracts	(0.7)		4.2		(4.9)
Total	$	(11.6)	$	15.8	$	(27.4)

	Year Ended December 31, 2019
	Total (loss) gain recognized in income		(Loss) gain realized in income on derivatives		Unrealized gain recognized in income on derivatives
Financial Instrument
	(Dollars in millions)
Foreign currency option contracts	$	(3.7)	$	(4.9)	$	1.2
Coal contracts related to forecasted sales	67.6		25.4		42.2
Coal trading contracts	(0.3)		(8.7)		8.4
Total	$	63.6	$	11.8	$	51.8

	Year Ended December 31, 2018
	Total (loss) gain recognized in income		(Loss) gain realized in income on derivatives		Unrealized (loss) gain recognized in income on derivatives
Financial Instrument
	(Dollars in millions)
Foreign currency option contracts	$	(9.1)	$	(8.4)	$	(0.7)
Coal contracts related to forecasted sales	115.7		97.4		18.3
Coal trading contracts	(2.9)		(5.3)		2.4
Total	$	103.7	$	83.7	$	20.0

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following tables set forth the hierarchy of the Company’s net financial asset positions for which fair value is measured on a recurring basis:

	December 31, 2020
	Level 1		Level 2		Level 3		Total
	(Dollars in millions)
Foreign currency option contracts	$	—	$	10.3	$	—	$	10.3
Coal contracts related to forecasted sales	—		(7.9)		—		(7.9)
Coal trading contracts	—		6.8		—		6.8
Equity securities	—		—		4.0		4.0
Total net financial assets	$	—	$	9.2	$	4.0	$	13.2
	December 31, 2019
	Level 1		Level 2		Level 3		Total
	(Dollars in millions)
Foreign currency option contracts	$	—	$	1.1	$	—	$	1.1
Coal contracts related to forecasted sales	—		21.2		—		21.2
Coal trading contracts	—		(16.4)		—		(16.4)
Equity securities	—		—		4.0		4.0
Total net financial assets	$	—	$	5.9	$	4.0	$	9.9

Carrying Amounts And Estimated Fair Values Of Company's Debt

The fair value of debt, shown below, is principally based on reported market values and estimates based on interest rates, maturities, credit risk, underlying collateral and completed market transactions.

	December 31,
	2020		2019
	(Dollars in millions)
Total debt at par value	$	1,591.3	$	1,367.2
Less: Unamortized debt issuance costs and original issue discount	(43.5)		(56.4)
Net carrying amount	$	1,547.8	$	1,310.8
Estimated fair value	$	987.6	$	1,271.1

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation

The following table summarizes the changes in the Company’s recurring Level 3 net financial assets:

	Year Ended December 31,
	2020		2019		2018
	(Dollars in millions)
Beginning of period	$	4.0	$	10.0	$	—
Included in earnings	—		(9.0)		(1.7)
Purchases	—		3.0		10.0
Settlements	—		—		1.7
End of period	$	4.0	$	4.0	$	10.0