Commitments and Contingencies - Supplemental balance sheet information related to the operating lease (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies.
Term of operating leases				3 years
Minimum lease payments by fiscal year
2024	$ 213	$ 292
Total future minimum lease payments	213	292
Less: Imputed interest	(8)	(14)
Present value of lease payments	205	278
Less: Current portion (included in other accrued expenses)	(205)	$ (278)	$ (257)
Noncurrent operating lease liability			$ 242
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]		Other Accrued Liabilities, Current	Other Accrued Liabilities, Current
Operating lease right-of-use asset	$ 198	$ 262	$ 475
Remaining lease term in years	8 months 12 days	10 months 24 days
Discount rate	10.00%	10.00%

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Discount rate used by lessee to determine present value of operating lease payments.

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

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for operating lease.

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

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

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

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Indicates line item in statement of financial position that includes current operating lease liability.

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

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Amount of lessee's right to use underlying asset under operating lease.

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