Share-Based Compensation (Details) - USD ($)				3 Months Ended
	Nov. 02, 2019	Dec. 21, 2018	Nov. 02, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value, exercises in period				$ 6,011,000
Employee Stock Ownership Plan (ESOP), Shares in ESOP		11,297,000
Common stock, par value (in USD per share)				$ 0.01		$ 0.01
Non-cash share-based compensation				$ 3,680,000	$ 4,525,000
Share-based Compensation expense				3,691,000	4,559,000
Compensation cost not yet recognized, period for recognition				6,141,000
Fair value of options vested				57,000
Proceeds from issuance of common stock				$ 4,046,000	68,000
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity incentive plan, number of shares authorized (shares)				5,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant				2,049,000
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity incentive plan, number of shares authorized (shares)				11,083,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant				1,704,000
Compensation cost not yet recognized, period for recognition				$ 8,009,000
Period for recognition for unrecognized compensation expense				2 years 2 months
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period for recognition for unrecognized compensation expense				2 years 1 month
Aggregate value			$ 25,000
Vested in period (shares)	1,159,000		1,197,000	1,159,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Stock Ownership Plan (ESOP), Shares in ESOP		5,000,000
Common stock, par value (in USD per share)		$ 0.01
Employee Stock Ownership Plan (ESOP), Compensation Expense				$ 39,000	$ 155,000
Shares issued under ESPP				56,000
Evoqua Water Technologies Corp. Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards vesting percentage				25.00%
Expiration period				10 years
Treasury Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares withheld related to net share settlement (including tax withholdings) (shares)	419,000			419,000	18,000