Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2019

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)	2019			2018
Balance at beginning of year	$	121.8		$	109.7
Accretion expense		5.6			5.1
Liabilities incurred and liabilities assumed in business combinations		0.6			4.6
Liabilities settled		(1.2	)		(2.8	)
Revisions in estimated cash flows		17.1			5.2
Balance at end of year	$	143.9		$	121.8

Schedule of Contractual Purchase Commitments

The Company’s contractual purchase commitments as of December 31, 2019 are as follows:

(in millions)
2020	$	140.6
2021		15.0
2022		3.0
2023		0.9
2024		0.9
Thereafter		15.9
Total	$	176.3

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 as of December 31, 2019 are as follows:

(in millions)	Contracts of Affreightment		Royalty Commitments
2020	$	15.8	$	15.7
2021		16.1		11.1
2022		16.3		10.3
2023		16.6		9.2
2024		16.9		8.9
Thereafter		52.2		59.7
Total	$	133.9	$	114.9