Revenue from Contracts with Customers (Current and Long-Term Contracts Outstanding) (Details)	Mar. 31, 2018 MMcf / d Boe / d $ / Mcf
Alberta AECO Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Fixed price (Cdn/MCF) | $ / Mcf	2.81
End Date, Q2, 2019 [Member] | United States [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes	4,000
End Date, Q3, 2019 [Member] | United States [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes	2,000
End Date, Q4, 2021, 2018 Deliveries [Member] | United States [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes	19,000
End Date, Q4, 2021, 2019-2021 Deliveries [Member] | United States [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes	13,000
End Date, Q4, 2020 [Member] | Canada [Member] | Alberta AECO Fixed Price [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes | MMcf / d	59
End Date, Q4, 2020 [Member] | Canada [Member] | USD Index Pricing [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes | MMcf / d	59