Segment Information - Assets (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Segment Reporting
Assets	$ 10,506.8	$ 10,694.1
Operating Segments \| Permian
Segment Reporting
Assets	2,382.6	2,096.8
Operating Segments \| North Texas
Segment Reporting
Assets	1,365.2	1,308.2
Operating Segments \| Oklahoma
Segment Reporting
Assets	3,906.6	3,209.5
Operating Segments \| Louisiana
Segment Reporting
Assets	2,626.8	2,734.5
Corporate
Segment Reporting
Assets	$ 225.6	$ 1,345.1

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Name:	us-gaap_Assets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant