Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2020

Asset Retirement Obligation [Abstract]

Asset Retirement Obligation Disclosure [Text Block]

	Asset Retirement Obligations
	September 30,		December 31,
	2020		2019
Balance Sheet line item	(in millions)
Current:
Asset retirement obligations, current liability	$	7.1	$	6.0
Long-term:
Asset retirement obligations	94.8		94.9
Total ARO Liability	$	101.9	$	100.9

Schedule of Change in Asset Retirement Obligation [Table Text Block]

The following is a reconciliation of the changes in the Company's ARO for the period specified below:

	Asset Retirement Obligations
	(in millions)
ARO liability at January 1, 2020	$	100.9
Accretion	2.9
Additions	1.1
Revisions	(0.5)
Liabilities related to assets sold	(1.4)
Liabilities settled	(1.1)
ARO liability at September 30, 2020	$	101.9