Fair Value Measurements Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Financial Assets
Derivative Asset, Netting Adjustments	[1]	$ 0.0	$ (0.4)
Derivative Asset, Net		6.7	123.2
Financial liabilities
Derivative Liability, Netting Adjustments	[1]	0.0	(0.4)
Derivative Liability, Net		61.8	0.7
Level 1 [Member]
Financial Assets
Derivative Asset, Fair Value, Gross		0.0	0.0
Financial liabilities
Derivative Liability, Fair Value, Gross		0.0	0.0
Fair Value, Inputs, Level 2 [Member]
Financial Assets
Derivative Asset, Fair Value, Gross		6.7	123.6
Financial liabilities
Derivative Liability, Fair Value, Gross		61.8	1.1
Level 3 [Member]
Financial Assets
Derivative Asset, Fair Value, Gross		0.0	0.0
Financial liabilities
Derivative Liability, Fair Value, Gross		0.0	0.0
Noncurrent Assets Held for Sale [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Assets
Derivative Asset, Fair Value, Gross			0.3
Long-term [Member]
Financial Assets
Derivative Asset, Netting Adjustments	[1]	0.0	0.0
Derivative Asset, Net		6.7	35.4
Financial liabilities
Derivative Liability, Netting Adjustments	[1]	0.0	0.0
Derivative Liability, Net		1.5	0.7
Long-term [Member] | Level 1 [Member]
Financial Assets
Derivative Asset, Fair Value, Gross		0.0	0.0
Financial liabilities
Derivative Liability, Fair Value, Gross		0.0	0.0
Long-term [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Assets
Derivative Asset, Fair Value, Gross		6.7	35.4
Financial liabilities
Derivative Liability, Fair Value, Gross		1.5	0.7
Long-term [Member] | Level 3 [Member]
Financial Assets
Derivative Asset, Fair Value, Gross		0.0	0.0
Financial liabilities
Derivative Liability, Fair Value, Gross		0.0	0.0
Short-term [Member]
Financial Assets
Derivative Asset, Netting Adjustments	[1]	0.0	(0.4)
Derivative Asset, Net		0.0	87.8
Financial liabilities
Derivative Liability, Netting Adjustments	[1]	0.0	(0.4)
Derivative Liability, Net		60.3	0.0
Short-term [Member] | Level 1 [Member]
Financial Assets
Derivative Asset, Fair Value, Gross		0.0	0.0
Financial liabilities
Derivative Liability, Fair Value, Gross		0.0	0.0
Short-term [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Assets
Derivative Asset, Fair Value, Gross		0.0	88.2
Financial liabilities
Derivative Liability, Fair Value, Gross		60.3	0.4
Short-term [Member] | Level 3 [Member]
Financial Assets
Derivative Asset, Fair Value, Gross		0.0	0.0
Financial liabilities
Derivative Liability, Fair Value, Gross		$ 0.0	$ 0.0

[1] The Company nets its derivative contract assets and liabilities outstanding with the same counterparty on the Condensed Consolidated Balance Sheets for the contracts that contain netting provisions. Refer to Note 7 – Derivative Contracts for additional information regarding the Company's derivative contracts.