SEGMENT REPORTING (Details)	12 Months Ended
SEGMENT REPORTING (Details)	Dec. 31, 2025 USD ($) segment	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Segment Reporting [Abstract]
Number of operating segment \| segment	1
Number of reportable segment \| segment	1
Costs and operating expenses:
Cost of goods sold	$ 4,745,000	$ 1,256,000	$ 0
Research and development
Research and development	71,433,000	103,738,000	125,046,000
Restructuring charges	17,032,000	0	0
Selling, general and administrative
Commercial expenses	159,256,000	145,732,000	69,135,000
Restructuring charges	17,032,000	0	0
Total costs and operating expenses	252,466,000	250,726,000	194,181,000
Loss from operations	(68,585,000)	(173,732,000)	(193,944,000)
Net loss	(83,500,000)	(174,572,000)	(184,127,000)
Product revenue, net
Revenues:
Total revenues	183,623,000	76,495,000	0
Royalties
Revenues:
Total revenues	258,000	499,000	$ 237,000
Reportable Segment
Revenues:
Total revenues	183,900,000	77,000,000.0
Costs and operating expenses:
Cost of goods sold	4,700,000	1,300,000
Selling, general and administrative
Other segment expenses	88,200,000	83,300,000
Total costs and operating expenses	252,500,000	250,700,000
Loss from operations	(68,600,000)	(173,700,000)
Total interest and other income (expense)	(14,900,000)	(900,000)
Net loss	(83,500,000)	(174,600,000)
Reportable Segment \| Research and development
Research and development
Restructuring charges	8,600,000	0
Selling, general and administrative
Restructuring charges	8,600,000	0
Reportable Segment \| Selling, general and administrative
Research and development
Restructuring charges	8,400,000	0
Selling, general and administrative
Restructuring charges	8,400,000	0
Reportable Segment \| Product revenue, net
Revenues:
Total revenues	183,600,000	76,500,000
Reportable Segment \| Royalties
Revenues:
Total revenues	300,000	500,000
Reportable Segment \| Research and clinical expenses
Research and development
Research and development	54,200,000	67,900,000
Reportable Segment \| Chemistry, manufacturing, and control expenses
Research and development
Research and development	9,800,000	26,200,000
Reportable Segment \| Commercial expenses
Selling, general and administrative
Commercial expenses	$ 78,600,000	$ 72,000,000.0

GERON CORP 10-K