Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2021

Asset Retirement Obligation Disclosure [Abstract]

Schedule of changes in asset retirement obligations

Changes in asset retirement obligations for the years ended December 31, 2021 and 2020 were as follows:

(In millions)	2021		2020
Balance at beginning of year	$	24.0	$	23.7
Accretion expense	0.8		0.9
Payments	(5.6)		(0.4)
Revisions of estimates	—		(0.2)
Divestiture	(0.2)		—
Balance at end of year	$	19.0	$	24.0