Summary of Significant Accounting Policies - Summary for Concentration of Receivables, Net Of Allowances, By Product or Service (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Revenue, Major Customer [Line Items]
Concentration of receivables, net of allowances	$ 47,026	$ 8,678
Product Concentration Risk [Member] \| Oil And Natural Gas And Related Products And Services [Member]
Revenue, Major Customer [Line Items]
Concentration of receivables, net of allowances	23,925	4,092
Product Concentration Risk [Member] \| Joint interest owners [Member]
Revenue, Major Customer [Line Items]
Concentration of receivables, net of allowances	22,661	4,586
Product Concentration Risk [Member] \| Miscellaneous other [Member]
Revenue, Major Customer [Line Items]
Concentration of receivables, net of allowances	$ 440

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.3-4)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 3

-Subparagraph a(1)

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 4

-Article 5

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