Restructuring and Cost Reduction Plan - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 4,010	$ 4,010
Restructuring and cost reduction plan
Restructuring Cost and Reserve [Line Items]
Percentage of corporate workforce eliminated due to restructuring	12.00%
Restructuring charges	$ 4,000
Restructuring and cost reduction plan | Scenario, Forecast
Restructuring Cost and Reserve [Line Items]
Expected future expense savings			$ 9,000