Valuation Method Used to Calculate Level 3 Liabilities Measured at Estimated Fair Value of Contingent Consideration Related to Acquisition (Detail) $ in Thousands	3 Months Ended
	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 10,331	$ 10,490
ECP Entwicklungsgesellschaft mbH | Discount Rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	21
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 10,331	$ 10,490
Level 3 | ECP Entwicklungsgesellschaft mbH
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Milestone Payment	15,000
Contingent consideration	10,331
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Milestone Payment	7,000
Contingent consideration	$ 5,712
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	2019
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone | Minimum | Various Upside and Downside Scenarios | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Probability of occurrence	10.00%
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	2022
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone | Maximum | Various Upside and Downside 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 | Discount Rate | Minimum | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	3.9
Level 3 | ECP Entwicklungsgesellschaft mbH | Probability weighted income approach | Clinical and regulatory milestone | Discount Rate | Maximum | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	4.2
Level 3 | ECP Entwicklungsgesellschaft mbH | Monte Carlo simulation model | Revenue-based milestone
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Milestone Payment	$ 8,000
Contingent consideration	$ 4,619
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	78.00%
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	2024
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
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	14
Level 3 | ECP Entwicklungsgesellschaft mbH | Monte Carlo simulation model | Revenue-based milestone | Expected Volatility for Forecasted Revenues | Contingent Consideration
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	50