Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values. Excludes accretion associated with asset retirement obligations.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Exit and Termination Costs - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
North Louisiana
Restructuring Cost And Reserve [Line Items]
Accretion expense			$ 22.1	$ 25.0
Exit and termination costs	$ 24.8	$ (28.2)
Total liability balance	414.2		414.2
Pennsylvania \| Capacity Releases on Transportation Pipelines
Restructuring Cost And Reserve [Line Items]
Total liability balance	$ 6.2		$ 6.2