For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13531-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Goodwill and Intangibles - Components of Intangible Assets Other Than Goodwill (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($) segment	Mar. 31, 2018	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016
Segment Reporting [Abstract]
Number of operating segments \| segment	1		1
Concentration Risk [Line Items]
Accounts receivable	$ 684.1		$ 651.8	$ 567.4
Product Sales
Concentration Risk [Line Items]
Accounts receivable	$ 83.5		$ 96.4	$ 88.0
Customer Concentration Risk \| Revenue \| Single Customer
Concentration Risk [Line Items]
Concentration risk	12.30%	11.30%	11.90%	12.90%	11.70%