FINANCE INCOME / EXPENSE (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 17, 2015
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Finance income        
Interest gain   $ 479 $ 60 $ 8
Gain arising for held-for-trading investments   923 3,619 13,453
Gain arising for held-to-maturity investments   0 0 4,941
Gain arising for available-for-sale investments   240 6,325 0
Foreign exchange gain   6,314 6,211 9,153
Subtotal   7,956 16,215 27,555
Finance expense        
Interest expense on borrowings   (95) (41) (108)
Loss arising for held-for-trading investments   (620) (2,966) 0
Foreign exchange loss $ (4,967) (9,043) (14,831) (19,289)
Other interest   (788) (776) (888)
Other   (490) (613) (667)
Subtotal   (11,036) (19,227) (20,952)
Finance (expense) income, net   (3,080) (3,012) 6,603
Other comprehensive income, net of tax, available-for-sale financial assets   $ 27 $ 52 $ (52)