Fair Value of Financial instruments - Schedule of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		$ 51,993
Fair Value, Recurring | Level 1 | U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 0	51,993
Fair Value, Recurring | Level 1 | Global Water Treatment Trust Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	15,058	12,054
Fair Value, Recurring | Level 2 | U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Recurring | Level 2 | Global Water Treatment Trust Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Recurring | Level 3 | U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value, Recurring | Level 3 | Global Water Treatment Trust Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 0	$ 0