Collaborations and Licensing Arrangements - Additional Information (Detail) - USD ($)			1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Mar. 29, 2019	Dec. 30, 2016	May 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Oct. 31, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized from collaborations and services				$ 14,595,000	$ 4,469,000	$ 47,045,000	$ 11,827,000
Deferred revenue - current				32,212,000		32,212,000		$ 36,885,000
Deferred revenue - long term				2,631,000		2,631,000		10,680,000
Commercial product sales
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized from collaborations and services				6,402,000	4,387,000	17,543,000	11,542,000
Collaboration and License Agreement | Receptor
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue				400,000		400,000
Proceeds from signing fees and upfront license fees		$ 1,300,000
Collaboration and License Agreement | United Therapeutics Corporation
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received									$ 45,000,000
Milestone Payment Received	$ 12,500,000
Revenue recognized from collaborations and services				7,900,000		23,300,000
Deferred revenue				32,200,000		32,200,000
Deferred revenue - current				31,500,000		31,500,000
Deferred revenue - long term				700,000		700,000
Total transaction price				100,400,000		100,400,000
Collaboration and License Agreement | United Therapeutics Corporation | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential milestone payments to be receive				37,500,000		37,500,000
Additional option exercise and development milestone payments to be receive				40,000,000		40,000,000
Research Agreement | United Therapeutics Corporation
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received					$ 10,000,000		$ 10,000,000
Revenue recognized from collaborations and services				200,000		5,900,000
Deferred revenue - current				400,000		400,000
Total transaction price				10,000,000		10,000,000
Research Agreement | United Therapeutics Corporation | Product Prototype
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total transaction price				9,000,000		$ 9,000,000
Revenue performance obligation, method used						The revenue for the product prototype is recognized using an output method (based on project milestones achieved and surveys of performance completed to date). The Company believes that this method best reflects the measure of progress toward complete satisfaction of the performance obligation.
Research Agreement | United Therapeutics Corporation | Engineering Consulting Services
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total transaction price				1,000,000		$ 1,000,000
Revenue performance obligation, method used						The revenue for the engineering consulting services is recognized using a ratable method until the obligation is satisfied and the Company believes that this method best reflects the measure of progress toward complete satisfaction of the performance obligation.
Research Agreement | United Therapeutics Corporation | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential milestone payments to be receive				30,000,000		$ 30,000,000
License and Distribution Agreement | Foreign Country | India Tax Authority
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Income Taxes Paid								$ 200,000
License and Distribution Agreement | Cipla Ltd
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue				2,000,000		2,000,000
Deferred revenue - current				$ 100,000		100,000
Marketing and distribution agreement date			2018-05
Supply and Distribution Agreement | Commercial product sales | Biomm
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized from collaborations and services						$ 700,000