Derivative Instruments - Gains (Losses) and Notional Volumes (Details) gal in Millions, MWh in Millions, MMBTU in Millions, $ in Millions |
3 Months Ended | |
|---|---|---|
|
Mar. 31, 2016
USD ($)
MMBTU
MWh
gal
|
Mar. 31, 2015
USD ($)
MMBTU
MWh
gal
|
|
| Realized Gain (Loss) on Derivatives, Net | ||
| Gains (Losses) | $ (31.6) | $ (5.1) |
| Natural gas contracts | ||
| Realized Gain (Loss) on Derivatives, Net | ||
| Gains (Losses) | $ (33.5) | $ (7.1) |
| Notional Volumes | ||
| Notional sales volumes (Dth or MWh) | MMBTU | 50.1 | 13.3 |
| Petroleum products contracts | ||
| Realized Gain (Loss) on Derivatives, Net | ||
| Gains (Losses) | $ (1.1) | $ (0.1) |
| Notional Volumes | ||
| Notional sales volumes (gallons) | gal | 3.0 | 0.9 |
| FTRs | ||
| Realized Gain (Loss) on Derivatives, Net | ||
| Gains (Losses) | $ 3.0 | $ 2.1 |
| Notional Volumes | ||
| Notional sales volumes (Dth or MWh) | MWh | 7.6 | 6.2 |