Commitments and Contingencies - (Tradipitant) - Additional Information (Detail) - Tradipitant - USD ($) $ in Millions	1 Months Ended	9 Months Ended	102 Months Ended
	Jul. 31, 2018	Sep. 30, 2020	Sep. 30, 2020
Commitments and Contingencies [Line Items]
Future percentage of royalty payments based net sales		low double digits
Development and milestone obligations paid to third party	$ 2.0		$ 3.0
Possible future milestone payment		$ 2.0
Sales Milestone
Commitments and Contingencies [Line Items]
Possible future milestone payment		80.0
U.S. | Regulatory Approval Milestone
Commitments and Contingencies [Line Items]
Possible future milestone payment		10.0
E.U. | Regulatory Approval Milestone
Commitments and Contingencies [Line Items]
Possible future milestone payment		$ 5.0