Oil and Gas Properties and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Proven Properties [Abstract]
Acquisition, equipment, exploration, drilling and environmental costs	$ 10,843,752	$ 10,752,642
Less: Accumulated depletion, depreciation and amortization	(9,770,832)	(9,742,176)
Proved	$ 1,072,920	$ 1,010,466

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

No definition available.

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