Oil and Gas Properties and Equipment - Schedule of Oil and Gas Properties and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Proven Properties:
Acquisition, equipment, exploration, drilling and abandonment costs	$ 11,471,499	$ 11,215,563
Less: Accumulated depletion, depreciation and amortization	(9,985,519)	(9,890,495)
Proven	$ 1,485,980	$ 1,325,068

Oil and gas properties, net of depletion, carried under the full cost method.

No definition available.

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