Goodwill and Acquired Intangible Assets (Narrative) (Details) $ in Millions	12 Months Ended
	Sep. 30, 2017 USD ($) segments	Sep. 30, 2016 USD ($) segments
Number of reportable segments | segments	3	3
Estimated aggregate future amortization expense for intangible assets, 2016	$ 58.1
Estimated aggregate future amortization expense for intangible assets, 2018	50.8
Estimated aggregate future amortization expense for intangible assets, 2019	48.0
Finite-Lived Intangible Assets, Amortization Expense, Year Four	42.5
Estimated aggregate future amortization expense for intangible assets, 2020	29.2
Estimated aggregate future amortization expense for intangible assets, thereafter	29.2
Solutions Group [Member]
Goodwill and acquired intangible assets	1,175.6	$ 1,196.6
IoT Group [Member]
Goodwill and acquired intangible assets	234.4	252.8
Professional Services [Member]
Goodwill and acquired intangible assets	$ 30.6	$ 30.7