Summary of Significant Accounting Policies (Treated Water Outsourcing) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Oct. 01, 2019	Sep. 30, 2019
Variable Interest Entity [Line Items]
Total current assets	$ 682,218		$ 637,220	$ 637,293
Operating Expenses	(87,468)	$ (95,129)
Income from operations	69,692	(6,359)
Property, plant, and equipment, net	339,135		335,710	333,584
Goodwill	397,006			392,890
Other non‑current assets	26,198			25,715
Liabilities	(1,395,172)		$ (1,418,175)	(1,372,026)
Treated Water Outsourcing
Variable Interest Entity [Line Items]
Cash	2,739			3,903
Total current assets	5,256			6,324
Revenues	2,642	3,156
Operating Expenses	(1,958)	(2,230)
Income from operations	684	$ 926
Property, plant, and equipment, net	1,442			2,186
Goodwill	2,206			2,206
Other non‑current assets	3			3
Liabilities	$ (2,353)			$ (2,388)