Suspended Exploratory Well Costs - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Extractive Industries [Abstract]
Capitalized exploratory well costs that have been capitalized for a period greater than one year	$ 0	$ 2,996

The amount of exploratory well costs that 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=68064819&loc=SL6806780-109447

Name:	us-gaap_CapitalizedExploratoryWellCostsThatHaveBeenCapitalizedForPeriodGreaterThanOneYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant