Accounting for derivative instruments and hedging activities - forecasted transactions (Details) kJ in Millions, MMBTU in Millions, $ in Millions |
9 Months Ended | 12 Months Ended |
|---|---|---|
|
Sep. 30, 2020
USD ($)
kJ
MMBTU
|
Dec. 31, 2019
USD ($)
kJ
MMBTU
|
|
| Natural gas swaps | ||
| Derivative instruments | ||
| Volume of forecasted transactions, energy (swaps: Mmbtu, agreements: joules) | MMBTU | 13.5 | 16.3 |
| Gas purchase agreements | ||
| Derivative instruments | ||
| Volume of forecasted transactions, energy (swaps: Mmbtu, agreements: joules) | kJ | 6.0 | 6.4 |
| Interest rate swaps | ||
| Derivative instruments | ||
| Volume of forecasted transactions, (in dollars) | $ | $ 421.6 | $ 468.4 |