Impairment and restructuring charges - Narrative (Details)	1 Months Ended				3 Months Ended			9 Months Ended		12 Months Ended
	Aug. 31, 2024 employee	May 31, 2024 positions employee	Aug. 31, 2023 employee	Jan. 31, 2023 employee	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Jun. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Restructuring Cost and Reserve [Line Items]
Impairment of long-lived assets					$ 0	$ 0	$ 27,200,000	$ 0	$ 27,200,000	$ 27,200,000
January 2023 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Workforce reduction | employee				125
Restructuring charges incurred since inception					9,300,000			9,300,000
Restructuring reserve					0			0
August 2023 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Workforce reduction | employee			400
Restructuring charges incurred since inception					19,400,000			19,400,000
Restructuring reserve					0			0
May 2024 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Workforce reduction | employee		300
Restructuring charges incurred since inception					18,500,000			18,500,000
Number of currently vacant positions eliminated | positions		85
August 2024 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Workforce reduction | employee	70
Restructuring charges incurred since inception					$ 2,500,000			$ 2,500,000