Commitments (Narrative) (Details) - Natural Gas [Member]	Mar. 31, 2017 MMcf / D MMcf / d CAD / Mcf
April to December 2017 [Member]
Commitments and Contingencies Disclosure [Line Items]
Notional amount, per day | MMcf / d	124
Swap price (per share)	2.97
January 2018 to December 2020 [Member]
Commitments and Contingencies Disclosure [Line Items]
Notional amount, per day | MMcf / D	59
Swap price (per share)	2.81