Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Numerator for basic and diluted earnings per common share—Net income attributable to Evoqua Water Technologies Corp.	$ 5,036	$ 7,812	$ 11,469	$ 60,957
Denominator:
Denominator for basic net income per common share—weighted average shares	118,882	116,459	118,882	116,459
Effect of dilutive securities:
Share‑based compensation	3,041	4,391	3,393	4,892
Denominator for diluted net income per common share—adjusted weighted average shares	121,923	120,850	122,275	121,351
Basic income per common share	$ 0.04	$ 0.07	$ 0.10	$ 0.52
Diluted income per common share	$ 0.04	$ 0.06	$ 0.09	$ 0.50