Segment Information - Assets (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Segment Reporting
Total identifiable assets	$ 9,055.1	$ 9,335.8
Operating Segments | Permian
Segment Reporting
Total identifiable assets	2,362.3	2,465.7
Operating Segments | North Texas
Segment Reporting
Total identifiable assets	1,091.0	1,135.8
Operating Segments | Oklahoma
Segment Reporting
Total identifiable assets	2,974.6	3,035.0
Operating Segments | Louisiana
Segment Reporting
Total identifiable assets	2,233.9	2,562.0
Corporate
Segment Reporting
Total identifiable assets	$ 393.3	$ 137.3