Financial Instruments (Notional Amounts and Fair Values of Derivatives Designated as Cash Flow Hedges and Derivatives Not Designated as Cash Flow Hedges) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Fair Value of assets for derivatives not designated as cash flow hedges	$ 19.6	$ 9.3
Fair Value of liability for derivatives not designated as cash flow hedges	1.5	2.9
Commodity Futures [Member]
Derivatives, Fair Value [Line Items]
Notional amount of derivatives not designated as cash flow hedges	136.8	142.5
Fair Value of assets for derivatives not designated as cash flow hedges	19.6	9.2
Fair Value of liability for derivatives not designated as cash flow hedges	0.2	1.8
Foreign Currency Exchanges [Member]
Derivatives, Fair Value [Line Items]
Notional amount of derivatives not designated as cash flow hedges	64.6	30.7
Fair Value of assets for derivatives not designated as cash flow hedges	0.0	0.1
Fair Value of liability for derivatives not designated as cash flow hedges	$ 1.3	$ 1.1