Term Deposits with Various Banks Outstanding (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Term deposits outstanding	$ 1,080	$ 6,830
Short-term investments
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Term deposits outstanding	690	6,600
Non-current assets
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Term deposits outstanding	$ 390	$ 230