Commitments and Contingencies (Details) gal in Thousands, $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2015 USD ($) MBoe pit	Dec. 31, 2008 gal
Crude Oil and Natural Gas
Long-term Purchase Commitment [Line Items]
Delivery commitments (MMBOE)	5,900
Mitchell County, Texas
Long-term Purchase Commitment [Line Items]
Number of sites \| pit	9
Anticipated cost of cleanup, remediation and related costs \| $	$ 2.9
Sylacauga, Talladega County, Alabama
Long-term Purchase Commitment [Line Items]
Gallons of wastewater transported \| gal		3

Total anticipated costs associated with remediation, site restoration, postclosure, monitoring commitments, or other exit costs that may occur on the sale, disposal, or abandonment of a particular property resulting from unanticipated contamination of the assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.Y.Q4)

-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section Y

-Paragraph Question 4

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