Acquisitions and Divestitures - Arkoma Divestiture - Assets Held for Sale - Impairment (Details) - USD ($) $ in Millions	6 Months Ended	9 Months Ended
Jun. 30, 2017	Sep. 30, 2017
Divestitures
Impairment charges		$ 148.0
Arkoma Assets \| Disposal Group, Held-for-sale, Not Discontinued Operations
Divestitures
Impairment charges	$ 148.0

The aggregate amount of write-downs for impairments recognized during the period for long-lived assets held for abandonment, exchange or sale.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2611-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

Name:	us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration