Exploratory Costs Exploratory Costs (Narrative) (Details)	Mar. 31, 2015	Mar. 31, 2014
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Number of projects with exploratory costs that have been suspended for a period greater than one year	0	0

The number of projects for which exploratory well costs have been capitalized for a period of greater than one year after the completion of drilling.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 1B

-Subparagraph b

-URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447

Name:	us-gaap_ProjectsThatHaveExploratoryWellCostsThatHaveBeenCapitalizedForPeriodGreaterThanOneYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant