Net Loss Per Share - Calculation of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended
	Jan. 06, 2022	Sep. 30, 2020	Mar. 31, 2022	Mar. 31, 2021
Numerator:
Net loss			$ (116,897)	$ (265,328)
Net loss attributable to non-controlling interests			498	360
Deemed dividend upon repurchase of preferred shares in consolidated subsidiary			(92,673)	0
Net loss attributable to common shareholders of Biohaven Pharmaceutical Holding Company Ltd., basic			(209,072)	(264,968)
Net loss attributable to common shareholders of Biohaven Pharmaceutical Holding Company Ltd., diluted			$ (209,072)	$ (264,968)
Denominator:
Weighted average common shares outstanding - basic (shares)			70,332,274	62,040,715
Weighted average common shares outstanding - diluted (shares)			70,332,274	62,040,715
Net loss per share attributable to common shareholders of Biohaven Pharmaceutical Holding Company Ltd. - basic (in dollars per share)			$ (2.97)	$ (4.27)
Net loss per share attributable to common shareholders of Biohaven Pharmaceutical Holding Company Ltd. - diluted (in dollars per share)			$ (2.97)	$ (4.27)
Other
Repurchase of preferred shares in consolidated subsidiary			$ 60,000
BioShin Limited
Other
Repurchase of preferred shares in consolidated subsidiary (in shares)	1,232,629
Repurchase of preferred shares in consolidated subsidiary	$ 152,673
Series A preferred shares | BioShin Preferred Shares
Other
Preferred stock issued and sold (in shares)		15,384,613