Summary of Future Minimum Rental Commitments (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Lessee Minimum Rental Commitments Payments Due [Abstract]
2019	$ 3,511
2020	2,804
2021	2,501
2022	2,455
2023	1,734
After 2023	2,495
Total lease payments	$ 15,500