Retirement Benefits (Schedule of Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan) (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Pension Plan [Member]
Changes in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 232,949	$ 208,101
Service cost	2,808	2,444	$ 2,802
Interest cost	6,965	6,873	8,084
Net actuarial (gains) losses	(11,455)	34,976
Contribution by participants	69	67
Benefits paid	(7,911)	(12,445)
Plan amendments	3,694	0
Settlements	0	47
Foreign currency exchange rate changes	380	(7,114)
Projected benefit obligation at end of year	227,499	232,949	208,101
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	208,812	196,253
Actual return (loss) on plan assets	22,609	30,061
Contributions by the Company	671	999
Contributions by plan participants	69	67
Benefits paid (plan assets)	(7,911)	(12,445)
Settlements	0	(47)
Foreign currency exchange rate changes	462	(6,076)
Fair value of plan assets at end of year	224,712	208,812	196,253
Net over/(under)funded status at end of year	(2,787)	(24,137)
Defined Benefit Pension Plan [Member] \| UNITED STATES
Changes in projected benefit obligation:
Projected benefit obligation at beginning of year	160,892	145,870
Service cost	1,675	1,695	2,018
Interest cost	5,757	5,236	5,956
Net actuarial (gains) losses	(5,267)	17,786
Contribution by participants	55	47
Benefits paid	(5,676)	(9,789)
Plan amendments	3,694	0
Settlements	0	47
Foreign currency exchange rate changes	0	0
Projected benefit obligation at end of year	161,130	160,892	145,870
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	145,886	135,590
Actual return (loss) on plan assets	20,067	19,859
Contributions by the Company	0	226
Contributions by plan participants	55	47
Benefits paid (plan assets)	(5,676)	(9,789)
Settlements	0	(47)
Foreign currency exchange rate changes	0	0
Fair value of plan assets at end of year	160,332	145,886	135,590
Net over/(under)funded status at end of year	(798)	(15,006)
Defined Benefit Pension Plan [Member] \| Foreign Plan [Member]
Changes in projected benefit obligation:
Projected benefit obligation at beginning of year	72,057	62,231
Service cost	1,133	749	784
Interest cost	1,208	1,637	2,128
Net actuarial (gains) losses	(6,188)	17,190
Contribution by participants	14	20
Benefits paid	(2,235)	(2,656)
Plan amendments	0	0
Settlements	0	0
Foreign currency exchange rate changes	380	(7,114)
Projected benefit obligation at end of year	66,369	72,057	62,231
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	62,926	60,663
Actual return (loss) on plan assets	2,542	10,202
Contributions by the Company	671	773
Contributions by plan participants	14	20
Benefits paid (plan assets)	(2,235)	(2,656)
Settlements	0	0
Foreign currency exchange rate changes	462	(6,076)
Fair value of plan assets at end of year	64,380	62,926	60,663
Net over/(under)funded status at end of year	(1,989)	(9,131)
Defined Benefit Pension Plan [Member] \| UNITED KINGDOM
Changes in projected benefit obligation:
Projected benefit obligation at end of year	55,306
Changes in fair value of plan assets:
Fair value of plan assets at end of year	52,810
Defined Benefit Pension Plan [Member] \| JAPAN
Changes in projected benefit obligation:
Projected benefit obligation at end of year	11,063
Changes in fair value of plan assets:
Fair value of plan assets at end of year	11,570
Other Postretirement Benefit Plans [Member]
Changes in projected benefit obligation:
Projected benefit obligation at beginning of year	35,630	34,927
Service cost	14	22	30
Interest cost	1,244	1,048	1,233
Net actuarial (gains) losses	(2,049)	1,912
Contribution by participants	1,365	1,299
Benefits paid	(3,964)	(3,503)
Foreign currency exchange rate changes	12	(75)
Projected benefit obligation at end of year	32,252	35,630	34,927
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	0	0
Contributions by the Company	2,599	2,204
Contributions by plan participants	1,365	1,299
Benefits paid (plan assets)	(3,964)	(3,503)
Fair value of plan assets at end of year	0	0	$ 0
Net over/(under)funded status at end of year	(32,252)	$ (35,630)
Other Postretirement Benefit Plans [Member] \| UNITED KINGDOM
Changes in projected benefit obligation:
Benefits paid	(21)
Projected benefit obligation at end of year	$ 409

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

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Amount of foreign currency translation gain (loss) which (increases) decreases benefit obligation of defined benefit plan.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of increase (decrease) in benefit obligation of defined benefit plan from change in terms of existing plan or initiation of new plan.

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Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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Amount of (increase) decrease to benefit obligation of defined benefit plan from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Includes, but is not limited to, lump-sum cash payment to participant in exchange for right to receive specified benefits, purchase of nonparticipating annuity contract and change from remeasurement.

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Amount of payment, which decreases plan assets of defined benefit plan, for irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Transaction constituting settlement includes, but is not limited to, making lump-sum cash payment to participant in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contract.

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