Concentrations of risks - Customer Concentration Risk (Details) - Customer Concentration Risk	3 Months Ended		9 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Sep. 30, 2025
Revenue from Contract with Customer Benchmark | Largest Customer
Concentration Risk [Line Items]
Concentration risk (as a percent)	14.70%	17.70%
Revenue from Contract with Customer Benchmark | Customer, Second Largest
Concentration Risk [Line Items]
Concentration risk (as a percent)	14.50%	14.40%
Revenue from Contract with Customer Benchmark | Customer, Third Largest
Concentration Risk [Line Items]
Concentration risk (as a percent)		10.80%
Revenue from Contract with Customer Benchmark | Customer, Fourth Largest
Concentration Risk [Line Items]
Concentration risk (as a percent)	12.10%
Accounts Receivable | Largest Customer
Concentration Risk [Line Items]
Concentration risk (as a percent)	26.00%		21.10%
Accounts Receivable | Customer, Second Largest
Concentration Risk [Line Items]
Concentration risk (as a percent)	13.50%		11.80%
Accounts Receivable | Customer, Third Largest
Concentration Risk [Line Items]
Concentration risk (as a percent)	10.30%