Share-based Compensation - Share-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total share-based compensation	$ 472	$ 332	$ 959	$ 662
Stock Option Awards [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total share-based compensation	310	232	624	455
Restricted Stock Units [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Total share-based compensation	$ 162	$ 100	$ 335	$ 207