Fair Value Measurements - Commodity and Foreign Currency Contracts (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Offsetting Assets [Line Items]
Gross Amounts Recognized	$ 191.0	$ 347.2
Gross Amounts Offset	131.7	254.8
Net Amounts Presented	59.4	92.4
Cash Collateral	2.8	27.1
Gross Amounts without Right of Offset	0.0	0.0
Net Amounts	56.6	65.3
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	155.8	332.5
Gross Amounts Offset	131.7	254.8
Net Amounts Presented	24.2	77.7
Cash Collateral	0.3	2.0
Gross Amounts without Right of Offset	0.0	0.0
Net Amounts	23.9	75.7
Commodity contracts
Offsetting Assets [Line Items]
Gross Amounts Recognized	176.3	331.2
Gross Amounts Offset	120.8	249.7
Net Amounts Presented	55.4	81.5
Cash Collateral	2.8	27.1
Gross Amounts without Right of Offset	0.0	0.0
Net Amounts	52.7	54.5
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	145.0	326.1
Gross Amounts Offset	120.8	249.7
Net Amounts Presented	24.2	76.5
Cash Collateral	0.3	2.0
Gross Amounts without Right of Offset	0.0	0.0
Net Amounts	23.9	74.5
Foreign currency contracts
Offsetting Assets [Line Items]
Gross Amounts Recognized	14.8	16.0
Gross Amounts Offset	10.8	5.1
Net Amounts Presented	3.9	10.9
Cash Collateral	0.0	0.0
Gross Amounts without Right of Offset	0.0	0.0
Net Amounts	3.9	10.9
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	10.8	6.4
Gross Amounts Offset	10.8	5.1
Net Amounts Presented	0.0	1.2
Cash Collateral	0.0	0.0
Gross Amounts without Right of Offset	0.0	0.0
Net Amounts	$ 0.0	$ 1.2