Acquisitions and Divestitures Other Divestitures (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Sale of Oil and Gas Property and Equipment	$ 13.8	$ 678.9	$ 243.6
Other Property [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Sale of Oil and Gas Property and Equipment	13.8	45.1	90.6
Gain (Loss) on Disposition of Oil and Gas and Timber Property	$ 1.2	$ 5.1	$ 38.5