Variable Interest Entities- Investments, Equity Method and Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Jul. 01, 2022	Apr. 01, 2022	Sep. 30, 2021	Apr. 08, 2021	Feb. 28, 2021	Oct. 01, 2019
Schedule of Equity Method Investments [Line Items]
Obligation to absorb risk of loss, percentage of partner's equity	100.00%		100.00%
Current assets	$ 832,220		$ 832,220				$ 678,458
Property, plant, and equipment, net	400,367		400,367				374,988
Goodwill	471,688		471,688				407,376
Intangible assets, net	315,983		315,983				290,075
Liabilities	(1,509,328)		(1,509,328)				(1,286,672)
Revenues	439,325	$ 369,681	1,232,321	$ 1,038,438
Operating Expenses	(105,917)	(90,121)	(314,233)	(259,606)
Operating profit (loss)	$ 31,030	28,310	$ 64,890	60,722
Frontier
Schedule of Equity Method Investments [Line Items]
Percentage of voting interests acquired					32.00%	32.00%		8.00%		60.00%
Remaining percentage to be acquired	40.00%		40.00%							32.00%
Frontier | Maximum
Schedule of Equity Method Investments [Line Items]
Remaining percentage to be acquired									10.00%
Treated Water Outsourcing
Schedule of Equity Method Investments [Line Items]
Partnership interest			50.00%
Cash							1,380
Current assets							3,202
Property, plant, and equipment, net							903
Goodwill							2,206
Liabilities							(1,009)
Revenues		843	$ 1,641	2,511
Operating Expenses		(748)	(1,440)	(2,217)
Operating profit (loss)		95	201	294
Frontier
Schedule of Equity Method Investments [Line Items]
Cash							2,095
Current assets							12,495
Property, plant, and equipment, net							2,113
Goodwill							1,798
Intangible assets, net							8,265
Liabilities							$ (9,425)
Revenues		4,945	13,363	7,793
Operating Expenses		(4,448)	(12,135)	(8,587)
Operating profit (loss)		$ 497	$ 1,228	$ (794)