Goodwill and Other Intangibles - Definite-Lived Intangible Assets (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2018	Sep. 30, 2017
Definite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 271.6	$ 263.3
Accumulated Amortization	(52.7)	(31.8)
Net Carrying Amount	218.9	231.5
Customer-related
Definite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	239.8	234.6
Accumulated Amortization	(39.0)	(23.7)
Net Carrying Amount	$ 200.8	210.9
Customer-related | Minimum
Definite-Lived Intangible Assets [Line Items]
Estimated Useful Life (years)	5 years
Customer-related | Maximum
Definite-Lived Intangible Assets [Line Items]
Estimated Useful Life (years)	13 years
Supplier-related
Definite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 3.2	1.5
Accumulated Amortization	(0.3)	(0.1)
Net Carrying Amount	$ 2.9	1.4
Supplier-related | Minimum
Definite-Lived Intangible Assets [Line Items]
Estimated Useful Life (years)	6 years
Supplier-related | Maximum
Definite-Lived Intangible Assets [Line Items]
Estimated Useful Life (years)	10 years
Trade name
Definite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 23.3	22.3
Accumulated Amortization	(11.2)	(7.0)
Net Carrying Amount	$ 12.1	15.3
Trade name | Minimum
Definite-Lived Intangible Assets [Line Items]
Estimated Useful Life (years)	2 years
Trade name | Maximum
Definite-Lived Intangible Assets [Line Items]
Estimated Useful Life (years)	10 years
Below-market leases
Definite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 0.7	0.7
Accumulated Amortization	(0.5)	(0.3)
Net Carrying Amount	$ 0.2	0.4
Below-market leases | Minimum
Definite-Lived Intangible Assets [Line Items]
Estimated Useful Life (years)	1 year
Below-market leases | Maximum
Definite-Lived Intangible Assets [Line Items]
Estimated Useful Life (years)	7 years
Non-compete agreements
Definite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 4.6	4.2
Accumulated Amortization	(1.7)	(0.7)
Net Carrying Amount	$ 2.9	$ 3.5
Non-compete agreements | Minimum
Definite-Lived Intangible Assets [Line Items]
Estimated Useful Life (years)	3 years
Non-compete agreements | Maximum
Definite-Lived Intangible Assets [Line Items]
Estimated Useful Life (years)	10 years