Retirement and Postretirement Benefit Plans (Schedule of Fair Value Measurements of Plan Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	$ 284.4	$ 267.0
Pension Plan [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	284.4	267.0	$ 219.1
Pension Plan [Member] | Cash [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	7.2	3.7
Pension Plan [Member] | U.S. companies [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	58.6	59.3
Pension Plan [Member] | International companies [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	59.4	56.4
Pension Plan [Member] | Fixed income securities [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	159.2	147.6
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	7.2	3.7
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Cash [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	7.2	3.7
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | U.S. companies [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | International companies [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | Pension Plan [Member] | Fixed income securities [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	0.0	0.0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	0.0	0.0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Cash [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	0.0	0.0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | U.S. companies [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	0.0	0.0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | International companies [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	0.0	0.0
Fair Value, Inputs, Level 2 [Member] | Pension Plan [Member] | Fixed income securities [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Cash [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | U.S. companies [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | International companies [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Pension Plan [Member] | Fixed income securities [Member]
Defined Benefit Plan, Plan Assets at Fair Value, Valuation Techniques and Inputs [Abstract]
Plan Assets	$ 0.0	$ 0.0