Lease Obligations (Operating Leases) (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Lease Term in Excess of One Year [Member]
Operating Leased Assets [Line Items]
Operating leases, rent and related expense (in dollars)	$ 26.9	$ 25.6
Lease Term in Excess of One Year [Member] \| Minimum [Member]
Operating Leased Assets [Line Items]
Operating leases, term of contract (in years)	1 year	1 year
Lease Term of One Year or Less [Member]
Operating Leased Assets [Line Items]
Operating leases, rent and related expense (in dollars)	$ 91.7	$ 55.1
Lease Term of One Year or Less [Member] \| Maximum [Member]
Operating Leased Assets [Line Items]
Operating leases, term of contract (in years)	1 year	1 year

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

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- Definition

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.

+ References

No definition available.

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- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41499-112717

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