Commitments (Narrative) (Details) - Natural Gas [Member]	Sep. 30, 2017 MMcf / D MMcf / d $ / Mcf CAD / Mcf
October to December 2017 [Member]
Commitments and Contingencies Disclosure [Line Items]
Notional amount, per day | MMcf / d	124
Swap price (per share) | CAD / Mcf	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) | CAD / Mcf	2.81
November 2017 to March 2018 [Member]
Commitments and Contingencies Disclosure [Line Items]
Notional amount, per day | MMcf / d	20
Swap price (per share) | $ / Mcf	3.51