Leases (Details) $ in Thousands					1 Months Ended	3 Months Ended		9 Months Ended
Leases (Details) $ in Thousands	Sep. 04, 2024 USD ($) ft²	Feb. 20, 2024 USD ($) ft²	Sep. 29, 2023 USD ($) ft²	Aug. 07, 2023 USD ($) ft²	Jan. 31, 2025	Sep. 30, 2025 USD ($) ft² item	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($) ft² item	Sep. 30, 2024 USD ($)
Lessee, Lease, Description [Line Items]
Sublease Income						$ 371	$ 332	$ 1,101	$ 632
Impairment of long-lived assets							4,795	2,637	5,233
Impairment expenses for right of use assets						0	$ 2,500	0	$ 2,500
Future minimum lease payments
2025						918		918
2026						3,757		3,757
2027						3,863		3,863
2028						3,973		3,973
2029						4,085		4,085
Thereafter						21,621		21,621
Total undiscounted lease payments						38,217		38,217
Less: imputed interest						(13,880)		(13,880)
Total lease liabilities						$ 24,337		$ 24,337
Employee Severance
Lessee, Lease, Description [Line Items]
Number of positions eliminated, period percent					55.00%			55.00%
Operating leases for office space
Lessee, Lease, Description [Line Items]
Area leased \| ft²						37,000		37,000
Option to extend lease								true
Number of extension terms \| item						2		2
Renewal term of lease						5 years		5 years
Option to terminate lease								true
Notice Period for termination lease								15 months
Sublease Agreement A
Lessee, Lease, Description [Line Items]
Area leased \| ft²				8,000
Option to extend lease				true
Sublease Income				$ 100
Annual increase in sublease rent (as a percent)				2.75%
Sublease Agreement B
Lessee, Lease, Description [Line Items]
Area leased \| ft²			29,000
Option to extend lease			true
Sublease Income			$ 900
1835 market street sublease agreement
Lessee, Lease, Description [Line Items]
Area leased \| ft²		16,000
Option to extend lease		true
Sublease Income		$ 300
Term of Contract		18 months
Operating leases for laboratory space
Lessee, Lease, Description [Line Items]
Option to terminate lease								true
Notice Period for termination lease								12 months
Sublease Agreement C
Lessee, Lease, Description [Line Items]
Area Subleased \| ft²	3,200
Subleased area of land	5.00%
Area leased \| ft²	62,000
Sublease Income	$ 100
Annual increase in sublease rent (as a percent)	2.50%
Maximum \| Operating leases for laboratory space
Lessee, Lease, Description [Line Items]
Number of extension terms \| item						2		2
Extended term of new lease agreement								5 years

Passage BIO, Inc. 10-Q