v3.25.1

Leases - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
Leases - Narrative (Details) - USD ($) $ in Thousands	Jul. 31, 2021	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2021
Lessee, Lease, Description [Line Items]
Operating lease agreement option to renewal term	5 years
Operating lease term					12 years
Total rent payments					$ 104,300
Initial monthly base rent on operating lease	$ 400
Option to extend lease	two
Reduction of security deposit in lieu of monthly payments				$ 3,600
Impairment of right-of-use asset			$ 45,800
Accretion and other lease related expenses		$ 1,100	1,000
Loss on lease termination		1,138	56,930
Current operating lease liability		9,463		13,006
Non-current operating lease liability		78,114		80,554
Seyon Lease
Lessee, Lease, Description [Line Items]
Construction allowance in operating lease	$ 26,000
Operating lease payments		7,100
Operating lease payments for rent from July through December 2024		4,900
Operating Lease, Liability		58,500		63,100
Current operating lease liability		$ 3,400		$ 7,100
Seyon Lease \| Tenant Improvement Allowance
Lessee, Lease, Description [Line Items]
Tenant improvement allowance receivable write-off			3,900
Construction in progress
Lessee, Lease, Description [Line Items]
Impairment charge			$ 6,200
Maximum
Lessee, Lease, Description [Line Items]
Estimated monthly base rent on operating lease	600
Letter of Credit
Lessee, Lease, Description [Line Items]
Security deposit	$ 3,600

Construction allowance in operating lease.

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- Definition

Estimated monthly base rent on operating lease

+ References

No definition available.

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- Definition

Initial monthly base rent on operating lease.

+ References

No definition available.

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- Definition

Amount of cash outflow from operating lease in litigation.

+ References

No definition available.

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- Definition

Reduction of lease security deposit in lieu of monthly payments.

+ References

No definition available.

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- Definition

Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values. Excludes accretion associated with asset retirement obligations.

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- Definition

Amount of direct write-downs of accounts receivable charged against the allowance.

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- Definition

Amount of gain (loss) on termination of lease before expiration of lease term.

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- Definition

For the asset that is reclassified back to held and used from held-for-sale, the amount of impairment charge that is recognized on the reclassification date.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Description of terms and conditions of option to extend lessee's operating lease that has not yet commenced. Includes, but is not limited to, information about option recognized as part of right-of-use asset and lease liability.

+ References

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- Definition

Term of lessee's operating lease renewal for lease not yet commenced, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease.

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- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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- Definition

Amount of loss from impairment of right-of-use asset from operating lease.

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- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

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- Definition

Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

+ References

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- Definition

Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.

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- Definition

Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.

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- Definition

The amount of an asset, typically cash, provided to a counterparty to provide certain assurance of performance by the entity pursuant to the terms of a written or oral agreement, such as a lease.

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Generation Bio Co. 10-Q