Subsequent Events (Details) $ in Thousands, CAD in Millions	1 Months Ended	3 Months Ended			4 Months Ended
	Apr. 30, 2016 CAD	Jun. 30, 2016 CAD	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2016 CAD
Subsequent Event [Line Items]
Proceeds from sales of property, plant and equipment | $			$ 33	$ 417,242
Northeastern British Columbia [Member]
Subsequent Event [Line Items]
Assets held for sale | $			$ 226,700
Scenario, Forecast [Member] | Syncrude Canada Ltd. [Member]
Subsequent Event [Line Items]
Percentae of interest sold					5.00%
Scenario, Forecast [Member] | Athabasca Oil Corporation [Member]
Subsequent Event [Line Items]
Cost of acquired assets		CAD 475
Cost of acquired assets, cash paid		250
Cost of acquired assets, carried interest		CAD 225
Cost of acquired assets, interest carry period		5 years
Scenario, Forecast [Member] | Kaybob Duvernay Lands, Alberta [Member] | Athabasca Oil Corporation [Member]
Subsequent Event [Line Items]
Interest in assets acquired		70.00%
Scenario, Forecast [Member] | Montney Lands, Alberta [Member] | Athabasca Oil Corporation [Member]
Subsequent Event [Line Items]
Interest in assets acquired		30.00%
Subsequent Event [Member] | Northeastern British Columbia [Member]
Subsequent Event [Line Items]
Proceeds from sales of property, plant and equipment	CAD 538
Gain recognition period	20 years
Subsidiary [Member] | Scenario, Forecast [Member] | Syncrude Canada Ltd. [Member]
Subsequent Event [Line Items]
Proceeds from sales of property, plant and equipment					CAD 937