Commitments and Contingencies - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands		Sep. 30, 2020	Mar. 31, 2020
Assets:
Total assets measured at fair value		$ 49
Liabilities:
Total liabilities measured at fair value			$ 227
Recurring [Member]
Assets:
Total assets measured at fair value		159,306	129,307
Liabilities:
Total liabilities measured at fair value		54	227
Recurring [Member] | Pension plan assets [Member]
Assets:
Total assets measured at fair value	[1]	14,585	12,436
Recurring [Member] | Short-term Investments [Member]
Assets:
Total assets measured at fair value	[2]	144,618	116,871
Recurring [Member] | Foreign currency forward contracts [Member]
Assets:
Total assets measured at fair value		103
Liabilities:
Total liabilities measured at fair value	[3]	54	227
Recurring [Member] | Level 1 [Member]
Assets:
Total assets measured at fair value		144,618	116,871
Recurring [Member] | Level 1 [Member] | Short-term Investments [Member]
Assets:
Total assets measured at fair value	[2]	144,618	116,871
Recurring [Member] | Level 2 [Member]
Assets:
Total assets measured at fair value		14,688	12,436
Liabilities:
Total liabilities measured at fair value		54	227
Recurring [Member] | Level 2 [Member] | Pension plan assets [Member]
Assets:
Total assets measured at fair value	[1]	14,585	12,436
Recurring [Member] | Level 2 [Member] | Foreign currency forward contracts [Member]
Assets:
Total assets measured at fair value		103
Liabilities:
Total liabilities measured at fair value	[3]	$ 54	$ 227

[1] The fair value of pension plan assets has been determined as the surrender value of the portfolio of active insured employees held within the AXA LLP Foundation Suisse Romande collective investment fund. See Note 10, “Defined Benefit Pension Plans”.

[2] The fair value of short-term investments has been determined based on the quoted value of the units held in the money market fund at the balance sheet date.  See Note 2, “Summary of Significant Accounting Policies – Short-term Investments”.

[3] The fair value of foreign currency forward contracts has been determined by calculating the present value of future cash flows, estimated using market-based observable inputs including forward and spot exchange rates and interest rate curves obtained from third party market price quotations.