Lease Commitments - Additional Information (Detail) $ in Thousands, £ in Millions	9 Months Ended
	Dec. 31, 2019 USD ($) ft² Sublease	Dec. 31, 2019 GBP (£) ft²	Mar. 31, 2019 USD ($)	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	$ 22,798
Operating lease liability	24,296
Operating lease liability, current	3,157
Finance lease right of use asset	1,975
Finance lease liability	1,472
Finance lease liability, current	522		$ 471
Other Non-current Assets [Member]
Lessee Lease Description [Line Items]
Rent deposit	$ 4,700	£ 3.6	$ 4,700
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