Fair Value Disclosure Fair Value Disclosure (Tables) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($) Instrument	Dec. 31, 2016 USD ($) Instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	$ (3.3)
Derivative, Notional Amount	290.2	$ 412.1
Cash Flow Hedge Pre Tax Gain Loss to be Reclassified within Twelve Months	(5.2)
Derivative, Net Liability Position, Aggregate Fair Value	23.7
Derivative Asset, Notional Amount	$ 450.0	$ 550.0
Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Number of Instruments Held | Instrument	11	9