Retirement and Postretirement Benefit Plans (Schedule of Obligations and Funded Status) (Details) - USD ($)	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Change in benefit obligation:
Benefit obligation at beginning of year	$ 371,800,000
Benefit obligation at end of year	363,800,000	$ 371,800,000
Change in plan assets:
Fair value of plan assets at beginning of year	291,700,000
Fair value of plan assets at end of year	301,900,000	291,700,000
Amounts recorded in the Consolidated Balance Sheets:
Accrued pension benefits, long-term	(73.8)	(89,300,000)
Pension Plan [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	371,800,000	380,400,000
Service cost	5,100,000	5,200,000
Interest cost	7,400,000	8,700,000	$ 12,500,000
Actuarial (gain) loss 1	(10,700,000)	28,700,000
Defined Benefit Plan, Benefit Obligation, Benefits Paid	12,600,000	12,600,000
Defined Benefit Plan, Benefit Obligation, Business Combination	0	3,500,000
Defined Benefit Plan, Benefit Obligation, Payment for Settlement	(200,000)	(44,200,000)
Defined Benefit Plan, Benefit Obligation, Special and Contractual Termination Benefits	3,300,000	500,000
Exchange rate (gain) loss	(300,000)	1,600,000
Benefit obligation at end of year	363,800,000	371,800,000	380,400,000
Change in plan assets:
Fair value of plan assets at beginning of year	291,700,000	310,600,000
Actual return on plan assets	21,800,000	33,400,000
Employer contributions	1,200,000	1,000,000.0
Defined Benefit Plan, Plan Assets, Benefits Paid	12,600,000	12,600,000
Defined Benefit Plan, Plan Assets, Business Combination	0	(3,500,000)
Defined Benefit Plan, Plan Assets, Payment for Settlement	(200,000)	(44,200,000)
Fair value of plan assets at end of year	301,900,000	291,700,000	$ 310,600,000
Funded status and net amounts recognized	(61,900,000)	(80,100,000)
Amounts recorded in the Consolidated Balance Sheets:
Accrued pension benefits, current portion	(1,400,000)	(1,500,000)
Accrued pension benefits, long-term	(60,500,000)	(78,600,000)
Net amount recognized	$ (61,900,000)	$ (80,100,000)