Basis of Presentation and Accounting Policies - Adjustments to Consolidated Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales	$ (903.6)	$ (886.4)
Gross profit	738.7	700.2
Selling, general and administrative expenses	(386.7)	(386.6)
Other income (expense)	(210.5)	4.2
Products and solutions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales	(782.4)	(780.5)
Services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales	$ (121.2)	(105.9)
As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		(889.5)
Gross profit		697.1
Selling, general and administrative expenses		(389.3)
Other income (expense)		10.0
As Reported | Products and solutions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		(783.2)
As Reported | Services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		(106.3)
Accounting Standards Update 2017-07 | Impact of adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		3.1
Gross profit		3.1
Selling, general and administrative expenses		2.7
Other income (expense)		(5.8)
Accounting Standards Update 2017-07 | Impact of adoption | Products and solutions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		2.7
Accounting Standards Update 2017-07 | Impact of adoption | Services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cost of sales		$ 0.4