Segment reporting (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Net Sales	$ 118,365	$ 94,626	$ 355,333	$ 312,497
Net Income (Loss)	5,228	5,859	20,047	16,919
Consolidation, Eliminations [Member]
Segment Reporting Information [Line Items]
Net Sales	(19,871)	(19,518)	(65,992)	(51,587)
Net Income (Loss)	(317)	(747)	(1,704)	(911)
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Net Sales	0	0	0	0
Net Income (Loss)	317	808	3,367	(1,317)
JingzhouHenglong Automotive Parts Co Ltd [Member]
Segment Reporting Information [Line Items]
Net Sales	55,790	57,530	191,093	195,940
Net Income (Loss)	689	3,771	6,300	13,389
Shashi Jiulong Power Steering Gears Co Ltd [Member]
Segment Reporting Information [Line Items]
Net Sales	26,067	17,787	75,525	54,976
Net Income (Loss)	478	1,083	3,739	2,219
Shenyang Jinbei Henglong Automotive Steering System Co Ltd [Member]
Segment Reporting Information [Line Items]
Net Sales	10,103	8,239	28,777	24,898
Net Income (Loss)	486	457	1,271	995
Wuhu Henglong Automotive Steering System Co Ltd [Member]
Segment Reporting Information [Line Items]
Net Sales	6,503	5,088	18,254	15,897
Net Income (Loss)	118	21	215	96
Hubei Henglong Automotive System Group Co Ltd [Member]
Segment Reporting Information [Line Items]
Net Sales	24,812	13,912	66,855	42,815
Net Income (Loss)	2,680	735	5,518	2,286
Other Sectors [Member]
Segment Reporting Information [Line Items]
Net Sales	14,961	11,588	40,821	29,558
Net Income (Loss)	777	(269)	1,341	162
Total Segments [Member]
Segment Reporting Information [Line Items]
Net Sales	138,236	114,144	421,325	364,084
Net Income (Loss)	$ 5,228	$ 5,798	$ 18,384	$ 19,147