Commitments and Contingencies - Summary of Restructuring Liability Recorded (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring liability	$ 74	$ 77
Accrued Liabilities [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring liability	42	33
Long-term Liabilities [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring liability	$ 32	$ 44