Fair Value Disclosure (Details Textual) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($) Instrument	Dec. 31, 2016 USD ($) Instrument	Dec. 31, 2015 USD ($)
Derivative [Line Items]
Operating assets and facilities, net	$ 6,192.1	$ 5,804.7
Fair Value Disclosure (Textual) [Abstract]
Derivative, Notional Amount	285.6	412.1
Cash Flow Hedge Pre Tax Gain Loss to be Reclassified within Twelve Months	(4.3)
Expected After tax reclassification of net losses from accumulated other comprehensive income to earnings in Next Twelve Months	2.7
Aggregate fair value of all derivative instruments with Net liability position	32.4
Derivative Asset, Notional Amount	$ 550.0	$ 550.0
Fair Value Hedging [Member]
Fair Value Disclosure (Textual) [Abstract]
Number of instruments, outstanding \| Instrument	10	8
Cash Flow Hedges [Member]
Fair Value Disclosure (Textual) [Abstract]
Number of instruments, outstanding \| Instrument	5	9
Other Nonoperating Income (Expense) [Member] \| Cash Flow Hedges [Member]
Fair Value Disclosure (Textual) [Abstract]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 38.9	$ (11.9)	$ (6.9)

Cash flow hedge pre-tax gain (loss) to be reclassified within twelve months.

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Fair value disclosure.

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Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
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Nominal or face amount used to calculate payments on the derivative asset.

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

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The number of derivative instruments of a particular group held by the entity.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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