Restructuring and Integration - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Severance costs	$ (260)	$ 0	$ 2,064	$ 17
Pay period for accrued restructuring and integration costs			2 years 4 months 25 days
Restructuring and Related Cost, Expected Cost Remaining	$ 0		$ 0
Corporate and Consolidations
Restructuring Cost and Reserve [Line Items]
Severance costs			$ 700