Acquisitions And Divestitures (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended
Apr. 30, 2013 Marcellus Shale In Pennsylvania [Member]	Sep. 30, 2014 Niobrara Formation In Colorado [Member] acre
Business Acquisition [Line Items]
Cost to acquire property	$ 93.0	$ 213.0
Area of land purchased		380,000

The cash outflow to purchase of mineral interests in oil and gas properties for use in the normal oil and gas operations and not intended for resale.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

Name:	us-gaap_PaymentsToAcquireOilAndGasProperty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration