Leases - Future Minimum Lease Payments Under Noncancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Operating Leases Future Minimum Payments
Operating Lease Payments, 2019	$ 2,581
Operating Lease Payments, 2020	2,632
Operating Lease Payments, 2021	2,628
Operating Lease Payments, 2022	883
Operating Lease Payments, Thereafter	0
Operating Lease Payments, Total minimum lease commitments	8,724
Sublease Rentals Future Payments Receivable
Sublease Rentals Receipts, 2019	1,365
Sublease Rentals Receipts, 2020	1,410
Sublease Rentals Receipts, 2021	1,454
Sublease Rentals Receipts, 2022	499
Sublease Rentals Receipts, Thereafter	0
Sublease Rentals Receipts, Total minimum lease commitments	4,728
Net, 2019	1,216
Net, 2020	1,222
Net, 2021	1,174
Net, 2022	384
Net, Thereafter	0
Net, Total minimum lease commitments	$ 3,996