Lease Commitments - Additional Information (Detail) $ in Thousands, £ in Millions	6 Months Ended
	Sep. 30, 2020 USD ($) ft² Sublease	Sep. 30, 2020 GBP (£) ft²	Mar. 31, 2020 USD ($)	Mar. 31, 2015
Lessee Lease Description [Line Items]
Number of sublease agreements | Sublease	0
Area of conventional reagents manufacturing facility | ft²	87,200	87,200
Lease commencement period	2018-03
Lease expiration period	2052-09
Lease term				5 years
Lessee, operating lease, extended term	5 years	5 years
Lessee, operating lease, option to extend, description	This lease was extended for a further five-year period to March 14, 2025
Lessee, operating lease, existence of option to extend	true
Lessee, operating lease, expiration date	Mar. 14, 2025
Operating lease right-of-use assets	$ 21,557		$ 21,493
Operating lease liability	23,420		22,947
Operating lease liability, current	3,138		3,033
Finance lease right of use asset	1,763		2,216
Finance lease liability	1,498		1,715
Finance lease liability, current	577		598
Other Non-current Assets [Member]
Lessee Lease Description [Line Items]
Rent deposit	$ 4,600	£ 3.6	$ 4,400
Minimum [Member]
Lessee Lease Description [Line Items]
Lease term	1 year	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Lease term	3 years	3 years