Net Loss Per Share - Calculation of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net loss	$ (172,937)	$ (62,304)
Denominator:
Weighted average common shares outstanding - basic and diluted (shares)	56,412,439	44,242,070
Net loss per share attributable to common shareholders of Biohaven Pharmaceutical Holding Company Ltd - basic and diluted (in dollars per share)	$ (3.07)	$ (1.41)