Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 114,395	$ (8,471)	$ 7,884
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation adjustments	(2,830)	1,507	(3,473)
Unrealized derivative (loss) gain on cash flow hedges, net of tax	(4,717)	74	(21)
Change in pension liability, net of tax	79	(5,568)	466
Total other comprehensive loss	(7,468)	(3,987)	(3,028)
Less: Comprehensive income attributable to non‑controlling interest	(746)	(1,052)	(1,749)
Comprehensive income (loss) attributable to Evoqua Water Technologies Corp.	$ 106,181	$ (13,510)	$ 3,107