Lease Obligations - Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Lessee, Operating Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract]
2025 (remaining)	$ 119
2026	1,153
2027	1,462
2028	1,506
2029	1,538
Thereafter	9,024
Total lease payments	14,802
Less imputed interest	(6,029)
Total	8,773	$ 8,861
Finance Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract]
2025 (remaining)	496
2026	1,520
2027	1,050
2028	486
2029	26
Thereafter	0
Total lease payments	3,578
Less imputed interest	(401)
Total	$ 3,177	$ 3,959

Finance Lease, Liability, to be Paid, After Year Four

No definition available.

Name:	bcrx_FinanceLeaseLiabilityToBePaidAfterYearFour
Namespace Prefix:	bcrx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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