Retirement and Postretirement Benefit Plans (Schedule of Obligations and Funded Status) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Change in benefit obligation:
Benefit obligation at beginning of year	$ 347.1
Special termination benefits	0.1	$ 0.0
Benefit obligation at end of year	345.8	347.1
Change in plan assets:
Fair value of plan assets at beginning of year	267.0
Fair value of plan assets at end of year	284.4	267.0
Amounts recorded in the Consolidated Balance Sheets:
Accrued pension benefits, long-term	(78.1)	(99.0)
Pension Plan [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	347.1	315.5
Service cost	5.8	5.0	$ 5.4
Interest cost	9.9	10.9	14.6
Actuarial loss (gain)	(5.7)	27.4
Benefits paid	(12.5)	(11.9)
Exchange rate loss	1.1	0.2
Benefit obligation at end of year	345.8	347.1	315.5
Change in plan assets:
Fair value of plan assets at beginning of year	267.0	219.1
Actual return on plan assets	28.8	28.8
Employer contributions	1.1	31.0
Benefits paid	(12.5)	(11.9)
Fair value of plan assets at end of year	284.4	267.0	$ 219.1
Funded status and net amounts recognized	(61.4)	(80.1)
Amounts recorded in the Consolidated Balance Sheets:
Accrued pension benefits, current portion	(1.2)	(1.1)
Accrued pension benefits, long-term	(60.2)	(79.0)
Net amount recognized	$ (61.4)	$ (80.1)