Retirement Benefits (Details 6) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	$ 3,447.9
Plan assets at end of year	3,788.3	$ 3,447.9
U.S. Pension Benefit Plans [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	2,616.2
Plan assets at end of year	2,890.1	2,616.2
Non-U.S. Pension Benefit Plans [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	831.7
Plan assets at end of year	898.2	831.7
Alternative equity [Member] | U.S. Pension Benefit Plans [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	56.9
Plan assets at end of year	61.0	56.9
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	85.4	69.1
Realized Gains (Losses)	0.0	0.0
Unrealized Gains (Losses)	(13.4)	14.5
Purchases, Sales, Issuances, and Settlements, Net	5.2	1.8
Plan assets at end of year	77.2	85.4
Fair Value, Inputs, Level 3 [Member] | Insurance contracts [Member] | U.S. Pension Benefit Plans [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	0.9	0.9
Realized Gains (Losses)	0.0	0.0
Unrealized Gains (Losses)	0.0	0.0
Purchases, Sales, Issuances, and Settlements, Net	0.0	0.0
Plan assets at end of year	0.9	0.9
Fair Value, Inputs, Level 3 [Member] | Insurance contracts [Member] | Non-U.S. Pension Benefit Plans [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	79.7	63.8
Realized Gains (Losses)	0.0	0.0
Unrealized Gains (Losses)	(13.4)	14.5
Purchases, Sales, Issuances, and Settlements, Net	5.2	1.4
Plan assets at end of year	71.5	79.7
Fair Value, Inputs, Level 3 [Member] | Other [Member] | Non-U.S. Pension Benefit Plans [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	4.8	4.4
Realized Gains (Losses)	0.0	0.0
Unrealized Gains (Losses)	0.0	0.0
Purchases, Sales, Issuances, and Settlements, Net	0.0	0.4
Plan assets at end of year	$ 4.8	$ 4.8