Revenues, Significant Customers and Concentrations of Risk - Summary of Significant Customers from which the Company Derived 10% or More of Total Revenue (Detail) - Customer Concentration Risk [Member]	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Teva [Member]
Concentration Risk [Line Items]
Total revenue by customer, percentage	42.00%	46.00%
AMAG [Member]
Concentration Risk [Line Items]
Total revenue by customer, percentage	16.00%	20.00%
AmerisourceBergen Corporation [Member]
Concentration Risk [Line Items]
Total revenue by customer, percentage	12.00%
AmerisourceBergen Corporation [Member] | Maximum [Member]
Concentration Risk [Line Items]
Total revenue by customer, percentage		10.00%
McKesson Corporation [Member]
Concentration Risk [Line Items]
Total revenue by customer, percentage	11.00%
McKesson Corporation [Member] | Maximum [Member]
Concentration Risk [Line Items]
Total revenue by customer, percentage		10.00%
Cardinal Health [Member]
Concentration Risk [Line Items]
Total revenue by customer, percentage	10.00%
Cardinal Health [Member] | Maximum [Member]
Concentration Risk [Line Items]
Total revenue by customer, percentage		10.00%
Ferring [Member]
Concentration Risk [Line Items]
Total revenue by customer, percentage		13.00%
Ferring [Member] | Maximum [Member]
Concentration Risk [Line Items]
Total revenue by customer, percentage	10.00%