Other Financial Information (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Apr. 30, 2016
Other Financial Information [Line Items]
Gain on sale of assets	$ 131,982	$ 22
Montney Natural Gas Fields [Member]
Other Financial Information [Line Items]
Deferred gain on sale of property	$ 176,700		$ 187,000
Deferred gain, period of recognition	20 years
Gain on sale of assets	$ 1,700

Amount of gain (loss) on sale or disposal of assets, including but not limited to property plant and equipment, intangible assets and equity in securities of subsidiaries or equity method investee.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2443-110228

Name:	us-gaap_GainLossOnDispositionOfAssets1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration