Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Deferred compensation plan assets
Mutual Funds	$ 15,432
Liabilities:
Option and purchase right	(10,396)	$ 0
Fair Value, Measurements, Recurring | Quoted Market Prices in Active Markets (Level 1)
Deferred compensation plan assets
Cash	1,052	1,251
Mutual Funds		17,806
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Assets:
Foreign currency forward contracts	112	24
Deferred compensation plan assets
Mutual Funds		0
Total return swaps—deferred compensation	250
Interest rate cap		3,127
Commodity swaps	(9)	19
Liabilities:
Pension plan	(44,344)	(46,013)
Deferred compensation plan liabilities	(24,191)	(24,382)
Total Return Swaps, Fair Value		(130)
Long‑term debt	(942,133)	(752,988)
Interest Rate Derivative Liabilities, at Fair Value		(303)
Foreign currency forward contracts	(33)	(102)
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Liabilities:
Earn-out liabilities related to acquisitions	(25)	(150)
Option and purchase right	(10,396)	(8,305)
Fair Value, Measurements, Recurring | Cash | Quoted Market Prices in Active Markets (Level 1)
Assets:
Defined benefit plan, fair value of plan assets	441	831
Fair Value, Measurements, Recurring | US Government Agencies Debt Securities
Assets:
Plan assets at net asset value	1,966	5,158
Fair Value, Measurements, Recurring | Liability Driven Investment
Assets:
Plan assets at net asset value	5,687	2,793
Fair Value, Measurements, Recurring | Guernsey Unit Trust
Assets:
Plan assets at net asset value	2,423	2,387
Fair Value, Measurements, Recurring | Global Absolute Return
Assets:
Plan assets at net asset value	2,106	2,225
Fair Value, Measurements, Recurring | Hedge Funds, Multi-strategy
Assets:
Plan assets at net asset value	14,182	15,244
Mar Cor
Deferred compensation plan assets
Earn Out asset	$ 7,824	$ 0