Valuation Method Used to Calculate Level 3 Liabilities Measured at Estimated Fair Value of Contingent Consideration Related to Acquisition (Detail) $ in Thousands	12 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 9,575	$ 10,490
ECP Entwicklungsgesellschaft mbH | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	0.21
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 9,575	$ 10,490
Level 3 | ECP Entwicklungsgesellschaft mbH
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	9,575
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 5,371
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone | Base Case Scenario | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Probability of occurrence	40.00%
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone | Minimum | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Projected fiscal year of milestone payments	2020
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone | Minimum | Various Downside and Upside Scenarios | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Probability of occurrence	15.00%
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone | Minimum | Discount Rate | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	0.038
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone | Maximum | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Projected fiscal year of milestone payments	2023
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone | Maximum | Various Downside and Upside Scenarios | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Probability of occurrence	40.00%
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone | Maximum | Discount Rate | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	0.040
Level 3 | ECP Entwicklungsgesellschaft mbH | Monte Carlo simulation model | Revenue-based milestone
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 4,204
Level 3 | ECP Entwicklungsgesellschaft mbH | Monte Carlo simulation model | Revenue-based milestone | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Probability of payment (risk neutral)	70.10%
Level 3 | ECP Entwicklungsgesellschaft mbH | Monte Carlo simulation model | Revenue-based milestone | Discount Rate | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	0.17
Level 3 | ECP Entwicklungsgesellschaft mbH | Monte Carlo simulation model | Revenue-based milestone | Measurement Input, Price Volatility | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	0.50
Level 3 | ECP Entwicklungsgesellschaft mbH | Monte Carlo simulation model | Revenue-based milestone | Minimum | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Projected fiscal year of milestone payments	2025
Level 3 | ECP Entwicklungsgesellschaft mbH | Monte Carlo simulation model | Revenue-based milestone | Maximum | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Projected fiscal year of milestone payments	2035