Condensed Consolidated Statements of Changes in Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 146,244	$ 193,001	$ 109,881
Operating activities
Net income (loss)	51,662	114,395	(8,471)
Reconciliation of net income to cash flows provided by operating activities:
Depreciation and amortization	113,664	107,268	98,236
Amortization of Debt Issuance Costs	3,280	4,026	2,612
Deferred income taxes	(2,363)	(1,234)	1,948
Share-based compensation	15,524	10,509	19,903
Loss (gain) on sale of property, plant, and equipment	1,287	950	(932)
Loss (gain) on sale of business	193	(68,051)	0
Foreign currency exchange (gains) losses on intercompany loans and other non-cash items	(1,094)	(8,202)	10,713
Changes in assets and liabilities
Accounts receivable	(13,281)	(6,844)	(13,235)
Inventories	(15,985)	(7,604)	(1,469)
Contract assets	8,426	(4,136)	(23,827)
Prepaids and other current assets	260	2,088	9,447
Accounts payable	9,824	8,017	9,408
Accrued expenses and other liabilities	21,881	22,078	(9,159)
Contract liabilities	28,447	(12,556)	21,311
Income taxes	(2,091)	592	(3,651)
Other non‑current assets and liabilities	(40,929)	15,730	12,362
Net cash provided by operating activities	178,705	177,026	125,196
Investing activities
Purchase of property, plant, and equipment	(75,293)	(88,456)	(88,869)
Purchase of intangibles	(3,780)	(6,529)	(6,426)
Proceeds from sale of property, plant, and equipment	2,041	1,191	3,636
Proceeds from Divestiture of Businesses, Net of Cash Divested	897	118,894	0
Payments to Acquire Businesses, Net of Cash Acquired	(21,037)	(13,108)	(2,873)
Net cash (used in) provided by investing activities	(97,172)	11,992	(94,532)
Financing activities
Issuance of debt, net of deferred issuance costs	761,915	21,959	38,381
Borrowings under credit facility	0	2,597	292,825
Repayment of debt	(898,024)	(117,131)	(307,809)
Finance Lease, Principal Payments	(13,396)	(13,441)	(12,900)
Payment of earn-out related to previous acquisitions	(170)	(470)	(461)
Proceeds from issuance of common stock	21,205	10,091	363
Taxes paid related to net share settlements of share-based compensation awards	(1,323)	(9,832)	(1,270)
Cash paid for interest rate cap	0	0	(2,235)
Distribution to non‑controlling interest	(551)	(1,890)	(1,150)
Net cash (used in) provided by financing activities	(130,344)	(108,117)	5,744
Effect of exchange rate changes on cash	2,054	2,219	(1,601)
Cash and cash equivalents classified as held for sale	0	0	(7,291)
Change in cash and cash equivalents	(46,757)	83,120	27,516
Cash and cash equivalents
Beginning of period		109,881	82,365
End of period			109,881
Supplemental disclosure of cash flow information
Cash paid for taxes	14,194	8,427	10,340
Cash paid for interest	26,502	38,680	52,786
Non‑cash investing and financing activities
Accrued earn-out related to acquisitions	0	204	0
Finance lease transactions	14,351	12,600	18,640
Operating Lease Obligation Incurred	12,894	23,727	0
Noncash put and mandatory call option	8,305	7,739	0
Landlord incentives	0	0	1,000
Cash divested with sale of business	$ 0	$ 12,117	$ 0