Fair value measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair value measurements [Abstract]

Summary of liabilities measured at fair value on recurring basis

	As of December 31, 2016
	Level 1		Level 2		Level 3		Total
Items
Investment - Available-for-sale securities		182,480		-		6,117		188,597

	As of December 31, 2017
	Level 1		Level 2		Level 3		Total
Items
Short-term investments		29,570		94,980		-		124,550
Investment - Available-for-sale securities		138,251		-		1,961		140,212
		167,821		94,980		1,961		264,762

Schedule of changes in level 3 instruments

	Level 3 Available-for-sale securities
Fair value as at January 1, 2016 and January 1, 2017		6,117
Other than temporary impairment		(6,117)
Addition		2,033
Foreign currency translation adjustment		(72)
Fair value as at December 31, 2017		1,961