Revenue from Contracts with Customers (Current Long-Term Contracts Outstanding) (Details)	Mar. 31, 2019 MMcf / d Boe / d
End Date, Q3, 2019 [Member] | United States [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes | Boe / d	4,000
End Date, Q4, 2021 [Member] | United States [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes | Boe / d	17,000
End Date, Q4, 2020 [Member] | Canada [Member] | Alberta AECO [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes	59
End Date, Q4, 2020 [Member] | Canada [Member] | USD Index Pricing [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes	60
End Date, Q4, 2024 [Member] | Canada [Member] | USD Index Pricing [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes	30
End Date, Q4, 2026 [Member] | Canada [Member] | USD Index Pricing [Member]
Disaggregation of Revenue [Line Items]
Approximate Net Volumes	38