Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Numerator for basic and diluted earnings per common share—Net income attributable to Evoqua Water Technologies Corp.	$ 13,155	$ 21,384	$ 24,624	$ 82,341
Denominator:
Denominator for basic net income per common share—weighted average shares	119,015	116,621	119,015	116,621
Effect of dilutive securities:
Share‑based compensation	3,245	3,595	3,312	4,432
Denominator for diluted net income per common share—adjusted weighted average shares	122,260	120,216	122,327	121,053
Basic income per common share	$ 0.11	$ 0.18	$ 0.21	$ 0.71
Diluted income per common share	$ 0.11	$ 0.18	$ 0.20	$ 0.68