Condensed Consolidated Statements of Changes in Cash Flows $ in Thousands	12 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 193,001	$ 109,881	$ 82,365
Operating activities
Net income (loss)	114,395	(8,471)	7,884
Reconciliation of net income (loss) to cash flows provided by operating activities:
Depreciation and amortization	107,268	98,236	85,860
Amortization of debt related costs (includes $1,795, $0 and $5,575 write off of deferred financing fees)	4,026	2,612	8,073
Deferred income taxes	(1,234)	1,948	(6,232)
Share-based compensation	10,509	19,903	15,742
Loss (gain) on sale of property, plant and equipment	950	(932)	(6,750)
Gain on sale of business	(68,051)	0	0
Foreign currency exchange (gains) losses on intercompany loans and other non-cash items	(8,202)	10,713	5,766
Changes in assets and liabilities
Accounts receivable	(6,844)	(13,235)	(3,139)
Inventories	(7,604)	(1,469)	(12,051)
Contract assets	(4,136)	(23,827)	(3,544)
Prepaids and other current assets	2,088	9,447	(3,773)
Accounts payable	8,017	9,408	24,945
Accrued expenses and other liabilities	3,410	(9,159)	(22,851)
Contract liabilities	(12,556)	21,311	(9,254)
Income taxes	592	(3,651)	2,777
Other non‑current assets and liabilities	15,730	12,362	(2,436)
Net cash provided by operating activities	158,358	125,196	81,017
Investing activities
Purchase of property, plant and equipment	(88,456)	(88,869)	(80,713)
Purchase of intangibles	(6,529)	(6,426)	(1,950)
Proceeds from sale of property, plant and equipment	1,191	3,636	21,641
Proceeds from sale of business, net of cash of $12,117, $0, and $0	118,894	0	430
Acquisitions, net of cash received of $0, $2,073, and $27	(13,108)	(2,873)	(146,443)
Net cash provided by (used in) investing activities	11,992	(94,532)	(207,035)
Financing activities
Issuance of debt, net of deferred issuance costs	21,959	38,381	155,270
Borrowings under credit facility	2,597	292,825	129,000
Repayment of debt	(117,131)	(307,809)	(242,470)
Repayment of finance lease obligation	(13,441)	(12,900)	(10,474)
Payment of earn-out related to previous acquisitions	(470)	(461)	(5,528)
Proceeds from issuance of common stock	18,927	363	137,605
Taxes paid related to net share settlements of share-based compensation awards	0	(1,270)	(8,807)
Stock repurchases	0	0	(230)
Cash paid for interest rate cap	0	(2,235)	0
Distribution to non‑controlling interest	(1,890)	(1,150)	(3,725)
Net cash (used in) provided by financing activities	(89,449)	5,744	150,641
Effect of exchange rate changes on cash	2,219	(1,601)	(1,512)
Cash and cash equivalents classified as held for sale	0	(7,291)	0
Change in cash and cash equivalents	83,120	27,516	23,111
Cash and cash equivalents
Beginning of period		82,365	59,254
End of period			82,365
Supplemental disclosure of cash flow information
Cash paid for taxes	8,427	10,340	4,450
Cash paid for interest	38,680	52,786	43,596
Non‑cash investing and financing activities
Accrued earn-out related to acquisitions	204	0	1,570
Finance lease transactions	12,600	18,640	10,595
Operating Lease Obligation Incurred	23,727	0	0
Noncash put and mandatory call option	7,739	0	0
Landlord incentives	$ 0	$ 1,000	$ 0