Segment reporting (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Net Product Sales	$ 114,417	$ 100,542	$ 271,156	$ 315,483
Net (Loss)/Income	1,513	4,201	(3,355)	7,542
Consolidation, Eliminations [Member]
Segment Reporting Information [Line Items]
Net Product Sales	(27,361)	(26,709)	(61,651)	(86,849)
Net (Loss)/Income	(64)	613	(1,328)	(1,718)
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Net Product Sales	0	0	0	0
Net (Loss)/Income	(678)	14	(1,766)	(1,450)
Jingzhou Henglong Automotive Parts Co., Ltd., "Henglong" [Member]
Segment Reporting Information [Line Items]
Net Product Sales	41,001	38,971	100,651	116,510
Net (Loss)/Income	193	1,300	(298)	1,379
Shashi Jiulong Power Steering Gears Co., Ltd., "Jiulong" [Member]
Segment Reporting Information [Line Items]
Net Product Sales	25,879	17,211	64,948	65,971
Net (Loss)/Income	823	(726)	(53)	1,637
Shenyang Jinbei Henglong Automotive Steering System Co., Ltd., "Shenyang" [Member]
Segment Reporting Information [Line Items]
Net Product Sales	3,622	4,267	9,860	14,573
Net (Loss)/Income	(5)	160	330	566
Wuhu Henglong Automotive Steering System Co., Ltd., "Wuhu" [Member]
Segment Reporting Information [Line Items]
Net Product Sales	3,221	3,047	8,742	14,283
Net (Loss)/Income	(100)	(190)	223	(577)
Hubei Henglong
Segment Reporting Information [Line Items]
Net Product Sales	37,014	33,664	76,565	89,423
Net (Loss)/Income	3,239	2,425	5,391	6,209
Hubei Henglong KYB Automobile Electric Steering System Co Ltd [Member]
Segment Reporting Information [Line Items]
Net Product Sales	14,298	15,971	32,987	54,803
Net (Loss)/Income	(2,045)	(426)	(3,484)	(2,280)
Other Entities [Member]
Segment Reporting Information [Line Items]
Net Product Sales	16,743	14,120	39,054	46,769
Net (Loss)/Income	150	1,031	(2,370)	3,776
Total Segments [Member]
Segment Reporting Information [Line Items]
Net Product Sales	141,778	127,251	332,807	402,332
Net (Loss)/Income	$ 2,255	$ 3,574	$ (261)	$ 10,710