Goodwill and Intangibles, net - Summary of Definite Lived Intangible Assets (Detail) - USD ($) $ in Millions	Sep. 30, 2016	Sep. 30, 2015
Finite-Lived Intangible Assets [Line Items]
Cost	$ 1,387.7	$ 1,389.2
Accumulated Amortization	(488.7)	(399.2)
Net	899.0	990.0
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	984.8	985.2
Accumulated Amortization	(302.9)	(247.4)
Net	681.9	737.8
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	165.7	165.4
Accumulated Amortization	(89.1)	(73.7)
Net	76.6	91.7
Technology-Based Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	237.2	238.6
Accumulated Amortization	(96.7)	(78.1)
Net	$ 140.5	$ 160.5