Revenue from contracts with customers - Narrative (Details) $ in Millions	Sep. 30, 2025 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, amount	$ 552.1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, amount	$ 87.5
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, amount	$ 80.7
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, amount	$ 383.9
Revenue, remaining performance obligation, expected timing of satisfaction, period
Pipeline
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract with customer, term (less than)	12 months
Pipeline | Firm Transportation Contract
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract weighted average remaining duration (less than)	5 years
Pipeline | Firm Storage Contract
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract weighted average remaining duration (less than)	2 years