Segment Information - Amortization Expense (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Assets	$ 9,335.8	$ 10,694.1
Operating Segments | Permian
Segment Reporting Information [Line Items]
Assets	2,465.7	2,096.8
Operating Segments | North Texas
Segment Reporting Information [Line Items]
Assets	1,135.8	1,308.2
Operating Segments | Oklahoma
Segment Reporting Information [Line Items]
Assets	3,035.0	3,209.5
Operating Segments | Louisiana
Segment Reporting Information [Line Items]
Assets	2,562.0	2,734.5
Corporate
Segment Reporting Information [Line Items]
Assets	$ 137.3	$ 1,345.1