Revenue from Contracts with Customers (Current Long-Term Contracts Outstanding) (Details)	Jun. 30, 2019 MMcf / d Boe / d
Q3 2019 | United States
Disaggregation of Revenue [Line Items]
Approximate Volumes | Boe / d	4,000
Q4 2021 | United States
Disaggregation of Revenue [Line Items]
Approximate Volumes | Boe / d	17,000
Q4 2020 | Canada | Contracts to sell natural gas at Alberta AECO fixed prices
Disaggregation of Revenue [Line Items]
Approximate Volumes	59
Q4 2020 | Canada | Contracts to sell natural gas at USD Index pricing
Disaggregation of Revenue [Line Items]
Approximate Volumes	60
Q4 2024 | Canada | Contracts to sell natural gas at USD Index pricing
Disaggregation of Revenue [Line Items]
Approximate Volumes	30
Q4 2026 | Canada | Contracts to sell natural gas at USD Index pricing
Disaggregation of Revenue [Line Items]
Approximate Volumes	38