Income Taxes Schedule of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Components of Deferred Tax Assets and Liabilities [Abstract]
Deferred Tax Liabilities, Property, Plant and Equipment	$ 1,135.0	$ 1,531.0
Deferred Tax Liabilities, Derivatives	0.0	60.4
Deferred Tax Liabilities, Net	1,135.0	1,591.4
Deferred Tax Assets Net Operating Loss And Tax Credit Carryforwards	161.6	51.9
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits	49.0	43.6
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Bonuses	11.4	7.0
Deferred Tax Assets, Derivative Instruments	74.3	0.0
Deferred Tax Assets, Other	12.8	9.1
Deferred Tax Assets, Gross	309.1	111.6
Deferred Tax Assets, Net of Valuation Allowance, Classification [Abstract]
Deferred Tax Liabilities, Net, Noncurrent	825.9	1,479.8
Deferred Tax Liabilities, Net	$ 825.9	$ 1,479.8