Financial Risk Management and Financial Instruments - Summary of Weightings Applied to Valuation Method (Details) |
12 Months Ended | |
|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| PWERM | ||
| Disclosure Of Financial Risk Management And Financial Instruments [Line Items] | ||
| Percentage of weightings | 50.00% | |
| Secondary Market Transactions | ||
| Disclosure Of Financial Risk Management And Financial Instruments [Line Items] | ||
| Percentage of weightings | 50.00% | |
| Bottom of Range | PWERM | ||
| Disclosure Of Financial Risk Management And Financial Instruments [Line Items] | ||
| Percentage of weightings | 50.00% | |
| Bottom of Range | Secondary Market Transactions | ||
| Disclosure Of Financial Risk Management And Financial Instruments [Line Items] | ||
| Percentage of weightings | 20.00% | |
| Top of Range | PWERM | ||
| Disclosure Of Financial Risk Management And Financial Instruments [Line Items] | ||
| Percentage of weightings | 80.00% | |
| Top of Range | Secondary Market Transactions | ||
| Disclosure Of Financial Risk Management And Financial Instruments [Line Items] | ||
| Percentage of weightings | 50.00% | |