Acquisition (Details) (Calico Energy, Inc. [Member], USD $) In Millions, unless otherwise specified	Feb. 07, 2012
Calico Energy, Inc. [Member]
Business Acquisition [Line Items]
Minority interest acquired	$ 1.3

This element represents the fair value of the noncontrolling interest in the acquiree at the acquisition date.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph p(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (e)(1)

-URI http://asc.fasb.org/extlink&oid=6910749&loc=d3e4845-128472

Name:	us-gaap_BusinessCombinationAcquisitionOfLessThan100PercentNoncontrollingInterestFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant