Undiscounted amount of the accrual for environmental loss contingencies.

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The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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Amount of cash outflow reducing loss contingency liability.

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Asset Retirement Obligations Contingencies - Gypstack (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Discounted asset retirement obligation	$ 1,749.3	$ 1,393.9	$ 1,315.2
Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Discounted asset retirement obligation	883.2	$ 669.9
2015 Consent Decrees With EPA \| Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Expected capital improvements and expenses	20.0
Asset retirement obligations, undiscounted	1,800.0
Discounted asset retirement obligation	$ 603.0