Represents the area of property subject to operating sublease.

No definition available.

Name:	fbio_AreaOfLandOperatingSublease
Namespace Prefix:	fbio_
Data Type:	dtr-types:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of base rent receivable from operating sublease .

+ References

No definition available.

+ Details

Name:	fbio_LesseeOperatingSubleaseBaseRentReceivable
Namespace Prefix:	fbio_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 40
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479092/842-20-40-1

+ Details

Name:	us-gaap_GainLossOnTerminationOfLease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_LesseeOperatingLeaseDescriptionAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 12
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-12

+ Details

Name:	us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	srt_ConsolidatedEntitiesAxis=fbio_MustangTherapeuticsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=fbio_WorcesterMassachusettsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitments and Contingencies (Narrative) (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Feb. 28, 2025 USD ($)	Mar. 31, 2026 USD ($)	Mar. 31, 2025 USD ($)	Feb. 10, 2026 USD ($) ft²
Lessee, Operating Lease, Description
Area of land \| ft²				23,000
Base rent receivable				$ 11,900
Net gain on lease termination		$ 0	$ 394
Mustang \| Worcester Massachusetts
Lessee, Operating Lease, Description
Proceeds from sale of fixed assets	$ 1,000
Net gain on lease termination	$ 400