Derivative Instruments and Hedging Activities - Amounts Included in OCI, Income and AOCI (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
---|---|---|---|---|
Jun. 30, 2018 |
Jun. 30, 2017 |
Jun. 30, 2018 |
Jun. 30, 2017 |
|
Revenues [Member] | ||||
Derivative Instruments, Gain (Loss) [Line Items] | ||||
Gain (loss) reclassified from OCI into income (effective portion) | $ (7.8) | $ 5.7 | $ (34.4) | $ (0.4) |
Commodity Contracts [Member] | Revenues [Member] | Not Designated as Hedging Instrument [Member] | ||||
Derivative Instruments, Gain (Loss) [Line Items] | ||||
Gain (loss) recognized in income on derivatives | (2.2) | (0.4) | (13.0) | (1.4) |
Cash Flow Hedging [Member] | Commodity Contracts [Member] | ||||
Derivative Instruments, Gain (Loss) [Line Items] | ||||
Gain (loss) recognized in OCI on derivatives (effective portion) | $ (103.0) | $ 29.8 | $ (38.3) | $ 96.0 |