Pension, Profit Sharing and Other Benefit Plans (Details) - USD ($)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2010
Defined Contribution Plans
Company contributions to defined contribution plan	$ 11,000,000.0	$ 19,400,000	$ 16,800,000
Equity securities | Minimum
Weighted-average assumptions used to determine net periodic benefit cost at the end of the year
Target allocation percentage	20.00%
Equity securities | Maximum
Weighted-average assumptions used to determine net periodic benefit cost at the end of the year
Target allocation percentage	55.00%
Debt securities | Minimum
Weighted-average assumptions used to determine net periodic benefit cost at the end of the year
Target allocation percentage	25.00%
Debt securities | Maximum
Weighted-average assumptions used to determine net periodic benefit cost at the end of the year
Target allocation percentage	75.00%
Cash equivalents | Minimum
Weighted-average assumptions used to determine net periodic benefit cost at the end of the year
Target allocation percentage	0.00%
Cash equivalents | Maximum
Weighted-average assumptions used to determine net periodic benefit cost at the end of the year
Target allocation percentage	55.00%
Real Estate | Minimum
Weighted-average assumptions used to determine net periodic benefit cost at the end of the year
Target allocation percentage	0.00%
Real Estate | Maximum
Weighted-average assumptions used to determine net periodic benefit cost at the end of the year
Target allocation percentage	10.00%
Defined Benefit Pension Plans
Defined Contribution Plans
Number of European employees covered by contributory defined benefit pension plan for which benefits were frozen (as a percent)				50.00%
Expected contribution to defined benefit pension plans in next fiscal year	$ 6,500,000
Unrecognized actuarial loss expected to be recognized in net pension cost over next fiscal year	(4,400,000)
Unrecognized actuarial loss expected to be recognized in net pension cost over next fiscal year, net of tax	3,600,000
Plan assets expected to be returned in 2020	0
Projected benefit obligation, ABO and fair value of plan assets for the defined benefit pension plans in which the ABO was in excess of the fair value of plan assets
Projected benefit obligation	251,892,000	246,697,000
Accumulated benefit obligation	251,892,000	246,697,000
Fair value of plan assets	232,132,000	221,311,000
Change in benefit obligations:
Net benefit obligation at the beginning of the year	246,697,000	222,332,000
Service cost	656,000	590,000	606,000
Interest cost	6,045,000	7,617,000	7,529,000
Actuarial loss	464,000	32,067,000
Gross benefits paid	(9,067,000)	(8,141,000)
Foreign currency exchange rate changes	7,097,000	(7,768,000)
Net benefit obligation at the end of the year	251,892,000	246,697,000	222,332,000
Change in plan assets:
Fair value of plan assets at the beginning of the year	221,311,000	214,530,000
Actual return on plan assets	7,302,000	17,794,000
Employer contributions	7,175,000	4,842,000
Gross benefits paid	(9,067,000)	(8,141,000)
PBGC Premium paid	(164,000)	(177,000)
Administrative expenses	(617,000)	(541,000)
Foreign currency exchange rate changes	6,192,000	(6,996,000)
Fair value of plan assets at the end of the year	232,132,000	221,311,000	214,530,000
Unfunded status of the plans	(19,760,000)	(25,386,000)
Unrecognized net actuarial loss	74,099,000	70,095,000
Net amount recognized	54,339,000	44,709,000
Amounts recognized in Accumulated OCI
Liability adjustment to OCI	(74,099,000)	(70,095,000)
Deferred tax asset	13,077,000	11,667,000
Valuation allowance on deferred tax asset	108,000	(1,172,000)
Accumulated other comprehensive loss	(60,914,000)	(59,600,000)
Components of net periodic pension cost (benefit)
Service cost	656,000	590,000	606,000
Interest cost	6,045,000	7,617,000	7,529,000
Expected return on plan assets	(11,770,000)	(11,990,000)	(14,120,000)
Amortization of actuarial loss	3,900,000	2,098,000	2,777,000
Administrative expenses	336,000	348,000	438,000
Net pension cost (benefit)	$ (833,000)	$ (1,337,000)	$ (2,770,000)
Weighted-average assumptions used to determine benefit obligation at the end of the year
Discount rate (as a percent)	2.10%	2.50%	3.60%
Rate of compensation increase (as a percent)	2.90%	3.10%	3.30%
Weighted-average assumptions used to determine net periodic benefit cost at the end of the year
Discount rate (as a percent)	2.50%	3.60%	3.30%
Expected return on plan assets (as a percent)	5.20%	5.70%	6.80%
Rate of compensation increase (as a percent)	3.10%	3.30%	3.20%
Defined Benefit Pension Plans | Equity securities
Change in plan assets:
Fair value of plan assets at the beginning of the year	$ 100,302,000
Fair value of plan assets at the end of the year	99,768,000	$ 100,302,000
Defined Benefit Pension Plans | Cash equivalents
Change in plan assets:
Fair value of plan assets at the beginning of the year	2,908,000
Fair value of plan assets at the end of the year	1,827,000	2,908,000
Defined Benefit Pension Plans | Real Estate
Change in plan assets:
Fair value of plan assets at the beginning of the year	3,564,000
Fair value of plan assets at the end of the year	13,601,000	3,564,000
Non-qualified deferred compensation plan
Deferred compensation plans
Liabilities associated with the non-qualified deferred compensation plan	9,600,000	11,000,000.0
Assets set aside to fund deferred compensation liabilities	$ 6,800,000	$ 6,600,000
Employee Stock Purchase Plan
Employee Stock Purchase Plan
ESPP discount rate (as a percent)	5.00%
Maximum annual employee contributions	$ 25,000