The expense recorded to reduce the value of oil and gas assets consisting of proved properties and unproved properties as the estimate of future successful production from these properties is reduced.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2921-110230

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 360
-Section 35
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=66906256&loc=d3e66150-109466

Name:	us-gaap_ImpairmentOfOilAndGasProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Oil and Natural Gas Properties (Details) - USD ($)	3 Months Ended		6 Months Ended
Oil and Natural Gas Properties (Details) - USD ($)	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Oil And Natural Gas Properties [Line Items]
Impairment of proved and unproved oil and gas properties			$ 0	$ 0
Proved Oil and Natural Gas Properties
Oil And Natural Gas Properties [Line Items]
Depletion expenses	$ 14,000,000	$ 10,700,000	$ 27,800,000	$ 20,300,000
Unproved Oil and Gas Properties \| Minimum
Oil And Natural Gas Properties [Line Items]
Unproved oil and gas lease term			3 years
Unproved Oil and Gas Properties \| Maximum
Oil And Natural Gas Properties [Line Items]
Unproved oil and gas lease term			5 years