Related Party Transactions - Summary of Related Party Expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Total related party expenses	$ 623	$ 1,146	$ 7,300
Pharmacovigilance | INC
Related Party Transaction [Line Items]
Total related party expenses	0	780	0
Avista | Advisory Services and Other Charges
Related Party Transaction [Line Items]
Total related party expenses	326	12	500
Avista | Termination Fee
Related Party Transaction [Line Items]
Total related party expenses	0	0	6,500
VWR | Inventory Supplies
Related Party Transaction [Line Items]
Total related party expenses	$ 297	$ 354	$ 300