Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 116.8		$ 122.9	$ 218.9	$ 237.7
Effective tax rate	23.00%		31.40%	22.10%	30.40%
Provision for income taxes, change in accounting method				$ 22.6
Provision for income taxes, adjustments to initial estimate impact of TCJA		$ 15.8

Effective Income Tax Rate Reconciliation, Change In Accounting Method, Software Development, Amount

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Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit)

+ References

No definition available.

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- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

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-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a),(b)
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-Name Accounting Standards Codification
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-Section S99
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-Subparagraph (SX 210.4-08.(h))
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