Share-Based Compensation - Expense by Types of Awards (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 6,369	$ 5,746
Restricted stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	102	1,015
Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 6,267	$ 4,731