Supplemental balance sheet information - Schedule of Gross Carrying Amounts and Accumulated Amortization of Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross	$ 1,101.8	$ 1,168.4
Accumulated Amortization	(838.5)	(848.2)
Net	263.3	320.2
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross	928.0	986.4
Accumulated Amortization	(670.5)	(680.8)
Net	257.5	305.6
Other
Finite-Lived Intangible Assets [Line Items]
Gross	173.8	182.0
Accumulated Amortization	(168.0)	(167.4)
Net	$ 5.8	$ 14.6

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 926
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-Section 50
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