Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Schedule of Changes in Asset Retirement Obligations

The following shows the changes in the asset retirement obligations:

years ended December 31 (in millions)	2020			2019
Balance at beginning of year	$	143.9		$	121.8
Accretion expense		5.9			5.6
Liabilities incurred and liabilities assumed in business combinations		0.3			0.6
Liabilities settled		(10.3	)		(1.2	)
Revisions in estimated cash flows		14.0			17.1
Balance at end of year	$	153.8		$	143.9

Schedule of Contractual Purchase Commitments

The Company’s contractual purchase commitments as of December 31, 2020 are as follows:

(in millions)
2021	$	137.0
2022		9.3
2023		7.6
2024		6.5
2025		6.6
Thereafter		58.2
Total	$	225.2

Schedule of Future Minimum Contracts of Affreightment and Royalty Commitments for All Noncancelable Agreements

Future minimum contracts of affreightment and royalty commitments for all noncancelable agreements that are not accounted for as leases on the Company’s consolidated balance sheet as of December 31, 2020 are as follows:

(in millions)	Contracts of Affreightment		Royalty Commitments
2021	$	16.4	$	18.0
2022		16.6		11.3
2023		16.9		10.4
2024		17.2		9.4
2025		17.4		8.9
Thereafter		35.7		61.7
Total	$	120.2	$	119.7