Pension and Post-retirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Pension Plans
Pension Plan and Retirement Benefits
Service cost	$ 1,385	$ 1,571	$ 4,153	$ 4,712
Interest cost	2,530	2,712	7,761	7,853
Expected return	(3,508)	(3,699)	(10,807)	(10,702)
Amortizations	1,268	3,029	3,851	9,004
Net periodic benefit cost	1,675	3,613	4,958	10,867
Postretirement Health Care Benefits
Pension Plan and Retirement Benefits
Service cost	83	87	251	261
Interest cost	1,078	1,073	3,234	3,219
Amortizations	750	1,070	2,250	3,210
Net periodic benefit cost	1,911	$ 2,230	5,735	$ 6,690
Contribution to plan			2,727
Expected future employer contribution	2,273		2,273
U.S. pension plan \| Defined Benefit Pension Plans
Pension Plan and Retirement Benefits
Contribution to plan			4,500
Expected future employer contribution	3,500		3,500
U.K. pension plan \| Defined Benefit Pension Plans
Pension Plan and Retirement Benefits
Contribution to plan			594
Expected future employer contribution	$ 210		$ 210

Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.

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Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(ii)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2709-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(iv)(01)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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+ References

No definition available.

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- Definition

Amount of contributions expected to be received by defined benefit plan from employer in fiscal year. Excludes contributions paid by employer in current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2709-114920

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- Definition

Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.

+ References

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

+ References

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Amount of net periodic benefit cost (credit) for defined benefit plan.

+ References

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

+ References

+ Details

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