Represents the amount of principal on f a debt instrument that can be converted to another debt instrument.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing after third 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).

+ References

No definition available.

+ Details

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Namespace Prefix:	omer_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of unamortized debt discount (premium) and debt issuance costs.

+ References

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing 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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Balance Type:	credit
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- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in third 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).

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in second 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).

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of long-term debt payable, sinking fund requirement, and other securities issued that are redeemable by holder at fixed or determinable price and date, maturing in remainder of current fiscal year.

+ References

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Details

Name:	us-gaap_DebtInstrumentAxis=omer_ConvertibleSeniorNotes2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=omer_TermLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Note 6 - Debt - Schedule of Debt Maturity (Details) - USD ($)	Jun. 30, 2025	May 14, 2025	May 13, 2025	Dec. 31, 2024	Jun. 03, 2024
2025	$ 0
2026	17,077,000
2027	0
2028	67,077,000
2029 and thereafter	70,785,000
Long-term	154,939,000
Net unamortized premiums, discounts, derivatives and issuance costs	12,865,000
Long-Term Debt, Gross	167,804,000
Convertible Senior Notes 2026 [Member]
2025	0
2026	17,077,000
2027	0
2028	0
2029 and thereafter	0
Total principal payments	17,077,000			$ 97,862,000	$ 14,900,000
Long-term	0			97,178
Net unamortized premiums, discounts, derivatives and issuance costs	(60,000)
Long-Term Debt, Gross	17,017,000	$ 17,100,000	$ 97,900,000	97,178,000
Term Loans [Member]
2025	0
2026	0
2027	0
2028	67,077,000
2029 and thereafter	0
Long-term	67,077,000
Net unamortized premiums, discounts, derivatives and issuance costs	20,236,000
Long-Term Debt, Gross	87,313,000
The 2029 Notes [Member]
2025	0
2026	0
2027	0
2028	0
2029 and thereafter	70,785,000
Total principal payments	70,785,000
Long-term	63,474			$ 0
Net unamortized premiums, discounts, derivatives and issuance costs	(7,311,000)
Long-Term Debt, Gross	$ 63,474,000