Revenue Recognition - Estimated Revenue Expected to be Recognized in Future Related to Performance Obligations (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction Price Allocated to the Remaining Performance Obligation as of September 30, 2019	$ 5,725
Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") | 2016 Agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction Price Allocated to the Remaining Performance Obligation as of September 30, 2019	$ 450
Expected Year By Which Revenue Recognition Will Be Completed	2021
Percentage of Revenue Recognized	96.00%
Daiichi Sankyo, Inc ("Daiichi") | 2016 Agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction Price Allocated to the Remaining Performance Obligation as of September 30, 2019	$ 2,485
Expected Year By Which Revenue Recognition Will Be Completed	2023
Percentage of Revenue Recognized	84.00%
Daiichi Sankyo, Inc ("Daiichi") | 2014 Agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction Price Allocated to the Remaining Performance Obligation as of September 30, 2019	$ 772
Expected Year By Which Revenue Recognition Will Be Completed	2020
Percentage of Revenue Recognized	98.00%
Bayer Pharma AG | 2016 Agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction Price Allocated to the Remaining Performance Obligation as of September 30, 2019	$ 2,018
Expected Year By Which Revenue Recognition Will Be Completed	2023
Percentage of Revenue Recognized	87.00%