License Agreement - Narrative (Details) - USD ($) $ in Thousands		2 Months Ended	12 Months Ended
	Apr. 29, 2016	Mar. 31, 2016	Mar. 31, 2018	Apr. 30, 2017	Mar. 31, 2017
Other Liabilities Disclosure [Abstract]
Shares issued to Takeda under the Takeda license agreement (in shares)	5,077,001
Period for which royalties are required to be paid after the first commercial sale of relugolix or MVT-602 products	10 years
Ownership percentage to which the warrants entitle Takeda	12.00%
Shares issued to settle the warrant liability to Takeda (in shares)				2,343,624	2,339,192
Acquisition of in-process research and development	$ 13,100	$ 0	$ 0		$ 13,117
Research and development expense, fair value of shares issued	7,700				$ 7,740
Takeda warrant liability	$ 5,400