Derivatives, Hedging Programs and Other Financial Instruments, Balance Sheet (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative asset	$ 14.1	$ 25.3
Derivative liability	(6.7)	(0.8)
Other Current Liabilities
Derivative [Line Items]
Derivative liability	(4.2)	(0.3)
Other Noncurrent Liabilities
Derivative [Line Items]
Derivative liability	(2.5)	(0.5)
Other Current Assets
Derivative [Line Items]
Derivative asset	11.5	18.9
Other Assets
Derivative [Line Items]
Derivative asset	$ 2.6	$ 6.4