Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the 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 350
-SubTopic 30
-Section 50
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The aggregate amount of recurring noncash expense charged against earnings in the period to allocate the cost of assets over their estimated remaining economic lives.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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Goodwill and Other Intangible Assets and Long-Lived Assets (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Aug. 01, 2016
Goodwill	$ 935.7		$ 935.7			$ 916.9	$ 98.5
Amortization	$ 7.2	$ 7.1	$ 21.7	$ 20.9
Customer Relationships [Member]
Weighted average amortization period			13 years
Minimum [Member] \| Trademarks [Member]
Intangible assets, useful life, minimum			1 year
Minimum [Member] \| Customer Relationships [Member]
Intangible assets, useful life, minimum			1 year
Maximum [Member] \| Trademarks [Member]
Intangible assets, useful life, minimum			4 years
Maximum [Member] \| Customer Relationships [Member]
Intangible assets, useful life, minimum			17 years
Scenario, Forecast [Member]
Amortization					$ 28.8