Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Reconciliation of Undiscounted Amount to Recorded Balance

The table below summaries our environmental liability accruals (in millions):

	December 31,
	2019		2018
Discounted environmental liabilities	$	59.5	$	58.7
Undiscounted environmental liabilities	86.6		84.6
Total accrued environmental liabilities	$	146.1	$	143.3

As of December 31, 2019, the estimated future payments of environmental obligations for which discounts have been applied are as follows (in millions):

2020	$	4.0
2021	3.0
2022	3.0
2023	4.0
2024	2.6
Thereafter	63.1
Discounted environmental liabilities, gross	79.7
Less: Discount applied	20.2
Discounted environmental liabilities	$	59.5

Schedule of Asset Retirement Obligations

The reconciliation of the beginning and ending carrying amounts of asset retirement obligations is as follows (in millions):

	December 31,
	2019			2018
Beginning balance	$	75.5		$	72.1
Liabilities identified	—			(1.2		)
Liabilities settled	(8.6		)	(2.2		)
Accretion expense	1.7			1.9
Reclassification from discontinued operations	—			4.9
Ending balance	$	68.6		$	75.5