Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Company contributions				$ 24.6	$ 31.0	$ 40.2
Defined Benefit Pension Plan | Minimum
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	$ 30.0			30.0
Defined Benefit Pension Plan | Maximum
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	40.0			40.0
International | Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Pension settlement loss	$ 0.0	$ 0.0		0.0	(0.2)
Prior service cost arising during period			$ 4.7
U.S. Supplementary Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Pension settlement loss				$ (1.8)	$ (6.3)