Derivatives and Risk Management Activities (Details 3) - Jun. 30, 2015 CAD in Millions, $ in Millions	USD ($) CAD / $	CAD CAD / $
Forward exchange contracts that exchange CAD for USD at the rate USD 1.00 to CAD 1.25 maturing in 2015
Currency Exchange Rate Risk Hedging:
Notional amount of derivatives	$ 208	CAD 260
Average exchange rate	1.25	1.25
Forward exchange contracts that exchange CAD for USD at the rate USD 1.00 to CAD 1.25 maturing in 2016
Currency Exchange Rate Risk Hedging:
Notional amount of derivatives	$ 30	CAD 38
Average exchange rate	1.25	1.25
Forward exchange contracts that exchange CAD for USD
Currency Exchange Rate Risk Hedging:
Notional amount of derivatives	$ 238	CAD 298
Forward exchange contracts that exchange USD for CAD at the rate USD 1.00 to CAD 1.24 maturing in 2015
Currency Exchange Rate Risk Hedging:
Notional amount of derivatives	$ 253	CAD 315
Average exchange rate	1.24	1.24
Forward exchange contracts that exchange USD for CAD at the rate USD 1.00 to CAD 1.22 maturing in 2016
Currency Exchange Rate Risk Hedging:
Notional amount of derivatives	$ 30	CAD 37
Average exchange rate	1.22	1.22
Forward exchange contracts that exchange USD for CAD
Currency Exchange Rate Risk Hedging:
Notional amount of derivatives	$ 283	CAD 352