Restructuring - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended			6 Months Ended
	Jun. 30, 2018	Apr. 30, 2017	Dec. 31, 2016	Jun. 30, 2018
Restructuring Cost And Reserve [Line Items]
Relieved cease-use liability				$ (2,222)
Corvallis Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring, initiation date				2016-03
Restructuring, completion date				Dec. 31, 2017
Corvallis Plan [Member] | Selling, General And Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Relieved cease-use liability	$ (2,200)
Corvallis Plan [Member] | Facility Closing [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses		$ 2,300	$ 1,500