Commitments and Contingencies - Summary of Restructuring Liability Recorded (Detail) - Discontinued Operations [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Restructuring Cost And Reserve [Line Items]
Restructuring liability	$ 107	$ 116
Accrued Liabilities [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring liability	36	35
Long-term Liabilities [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring liability	$ 71	$ 81