Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
Provision (benefit) for income taxes	$ 221	$ (59)	$ 1,091	$ 687
Net loss	173,443	160,304	593,267	659,579
Operating Segments | Reportable Segment
Segment Reporting Information [Line Items]
Preclinical research programs R&D Expense	16,675	13,977	58,608	40,921
R&D personnel expense (excluding share-based compensation)	20,473	18,289	62,100	55,491
R&D Share-based compensation expense	13,947	7,164	62,291	35,526
R&D Knopp amendment expense	0	0	0	171,850
G&A personnel expense (excluding share-based compensation)	6,276	6,288	18,755	18,798
G&A Share-based compensation expense	7,588	4,996	33,118	23,743
Other segment items	21,291	16,010	58,950	43,378
Non-operating loss (income)	3,840	(17,805)	(10,468)	(36,288)
Provision (benefit) for income taxes	221	(59)	1,091	687
Net loss	173,443	160,304	593,267	659,579
Operating Segments | BHV-4157 (Troriluzole) | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	10,769	14,774	38,802	48,937
Operating Segments | BHV-2000 (Taldefgrobep Alfa) | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	4,489	20,186	18,719	49,062
Operating Segments | BHV-7000 & BHV-7010 (Kv7) | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	29,671	44,370	92,415	96,575
Operating Segments | BHV-2100 & BHV-2110 (TRPM3 Antagonist) | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	2,720	5,386	26,314	14,278
Operating Segments | BHV-8000 (TYK2/JAK1) | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	4,134	3,064	29,722	9,989
Operating Segments | BHV-1300 (IgG Degrader) | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	8,628	8,745	28,980	25,328
Operating Segments | BHV-1310 (IgG Degrader) | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	369	2,461	5,055	9,659
Operating Segments | BHV-1400 (IgA Degrader) | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	8,049	4,591	19,646	16,295
Operating Segments | BHV-1600 (β1-AR AAB Degrader) | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	1,977	4,145	6,786	7,970
Operating Segments | BHV-1510 (TROP-2) | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	9,327	3,072	19,200	25,700
Operating Segments | BHV-1530 (FGFR3) | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	2,437	0	21,006	0
Operating Segments | Other R&D program expense | Reportable Segment
Segment Reporting Information [Line Items]
Direct R&D program expense	562	650	2,177	1,680
Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment
Segment Reporting Information [Line Items]
Net loss	$ 0	$ 0	$ 0	$ 0