Bank and government loans (Details Textual) $ in Thousands, ¥ in Millions				1 Months Ended
		May 05, 2017 USD ($)	Jul. 07, 2016 USD ($)	Aug. 17, 2017 USD ($)	Apr. 25, 2017 USD ($)	Apr. 20, 2017 USD ($)	Mar. 03, 2017 USD ($)	Mar. 03, 2017 CNY (¥)	Sep. 26, 2016 USD ($)	Aug. 26, 2016 USD ($)	May 06, 2016 USD ($)	Apr. 30, 2016 USD ($)	Jul. 16, 2014 USD ($)	May 22, 2012 USD ($)	May 18, 2012 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2017 CNY (¥)	Aug. 17, 2017 CNY (¥)	May 05, 2017 CNY (¥)	Apr. 28, 2017 USD ($)	Apr. 28, 2017 CNY (¥)	Apr. 21, 2017 USD ($)	Apr. 21, 2017 CNY (¥)	Dec. 31, 2016 USD ($)	Sep. 26, 2016 CNY (¥)	Aug. 26, 2016 CNY (¥)	Jul. 07, 2016 CNY (¥)	May 06, 2016 CNY (¥)	Jul. 22, 2014 USD ($)	Jul. 22, 2014 CNY (¥)	May 22, 2012 CNY (¥)
Debt Instrument [Line Items]
Short-term Debt, Weighted Average Interest Rate																4.70%	4.70%							5.20%
Non Revolving Credit Facility																								$ 30,000
Financing Receivable, Net																$ 40,400	¥ 268.3							$ 36,000
Time Deposits																2,100	¥ 13.9
Short-term Debt, Total				$ 3,000														¥ 20.0				$ 1,500	¥ 10.0
Debt Instrument, Collateral Amount				$ 3,000														¥ 20.0
Line of Credit Facility, Expiration Date				Aug. 16, 2018					Sep. 26, 2017
Letters of Credit Outstanding, Amount																23,900
Line of Credit Facility, Maximum Borrowing Capacity									$ 25,600																¥ 170.0
ICBC Macau [Member]
Debt Instrument [Line Items]
Non Revolving Credit Facility		$ 20,000													$ 30,000
Line of Credit Facility, Interest Rate Description															three-month LIBOR plus 2.25
Line of Credit, Current		23,400													$ 31,600
Line of Credit Facility, Expiration Date															Nov. 03, 2012
Taishin Bank [Member]
Debt Instrument [Line Items]
Non Revolving Credit Facility					$ 10,000
Line of Credit Facility, Interest Rate at Period End					2.70%
Financing Receivable, Net																10,000
Line of Credit Facility, Expiration Date					Apr. 25, 2018
Credit Facility [Member] | Taishin Bank [Member]
Debt Instrument [Line Items]
Financing Receivable, Net																				$ 12,000	¥ 79.4
Line of Credit, Current																				9,900
Debt Instrument, Collateral Amount					$ 10,000															10,000
Henglong CITIC Credit Facility [Member]
Debt Instrument [Line Items]
Financing Receivable, Net		23,900																	¥ 158.9
Hubei Henglong CITIC Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Expiration Date									Sep. 26, 2017
Industrial and Commercial Bank Of China Macau [Member]
Debt Instrument [Line Items]
Non Revolving Credit Facility						$ 20,000								$ 30,000
Line of Credit Facility, Interest Rate Description						LIBOR plus 1.30% per annum								LIBOR plus 0.7% per annum
Line of Credit Facility, Interest Rate at Period End																								1.70%
Financing Receivable, Net														$ 32,600																	¥ 207.1
Arrangement Fee														100
Line of Credit, Current						$ 23,900								31,600
Line of Credit Facility, Expiration Date						May 12, 2018
Industrial and Commercial Bank Of China Jingzhou Branch [Member]
Debt Instrument [Line Items]
Arrangement Fee		$ 40
HSBC Bank China Company Limited [Member]
Debt Instrument [Line Items]
Non Revolving Credit Facility													$ 5,000																$ 5,000
Line of Credit Facility, Interest Rate Description			LIBOR plus 0.8% per annum
Line of Credit Facility, Interest Rate at Period End			1.95%										1.70%														1.95%
Line of Credit, Current			$ 5,100										$ 5,400																5,400
Time Deposits			$ 5,200																								¥ 36.0		$ 4,800	¥ 33.0
Line of Credit Facility, Expiration Date													Jul. 01, 2015
Chinese government loan [Member]
Debt Instrument [Line Items]
Short-term Debt, Total	[1]															4,520								$ 3,604
Debt Instrument, Collateral Amount																						$ 1,500	¥ 10.0
HSBC Bank Brazil [Member]
Debt Instrument [Line Items]
Line of Credit, Current												$ 100
Debt Instrument, Interest Rate, Stated Percentage											8.20%																	8.20%
Debt Instrument, Collateral Amount											$ 100	$ 100																¥ 0.5
Line of Credit Facility, Expiration Date											Oct. 09, 2017	Oct. 27, 2017
Letters of Credit Outstanding, Amount											$ 100
Debt Instrument, Face Amount											$ 100
China CITIC Bank [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End									4.99%																4.99%
Financing Receivable, Net																12,000
Short-term Debt, Total	[2]															$ 28,796								$ 0
Line of Credit Facility, Maximum Borrowing Capacity | ¥																									¥ 100.0
China CITIC Bank [Member] | Henglong CITIC Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End									4.99%																4.99%
China CITIC Bank [Member] | Hubei Henglong CITIC Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate at Period End									5.00%																5.00%
Line of Credit Facility, Maximum Borrowing Capacity									$ 15,100
China CITIC Bank [Member] | Hubei Henglong CITIC Credit Facility [Member] | Line Of Credit Maturity On 50218 [Member]
Debt Instrument [Line Items]
Proceeds from Lines of Credit							$ 4,900	¥ 32.5
China CITIC Bank [Member] | Hubei Henglong CITIC Credit Facility [Member] | Line Of Credit Maturity On 60218 [Member]
Debt Instrument [Line Items]
Proceeds from Lines of Credit							4,900	32.5
China CITIC Bank [Member] | Hubei Henglong CITIC Credit Facility [Member] | Line Of Credit Maturity On 70218 [Member]
Debt Instrument [Line Items]
Proceeds from Lines of Credit							4,600	30.6
China CITIC Bank [Member] | Hubei Henglong CITIC Credit Facility [Member] | Line Of Credit Maturity On 20218 [Member]
Debt Instrument [Line Items]
Proceeds from Lines of Credit							4,300	28.7
China CITIC Bank [Member] | Hubei Henglong CITIC Credit Facility [Member] | Line Of Credit Maturity On 80218 [Member]
Debt Instrument [Line Items]
Proceeds from Lines of Credit							4,300	28.7
China CITIC Bank [Member] | Hubei Henglong CITIC Credit Facility [Member] | Line Of Credit Maturity On 90218 [Member]
Debt Instrument [Line Items]
Proceeds from Lines of Credit							$ 5,800	¥ 38.2
Bank of China Brazil [Member]
Debt Instrument [Line Items]
Line of Credit, Current										$ 600										$ 600
Debt Instrument, Interest Rate, Stated Percentage										4.00%																4.00%
Debt Instrument, Collateral Amount										$ 900
Line of Credit Facility, Expiration Date										Jan. 15, 2018
Letters of Credit Outstanding, Amount										$ 900
Debt Instrument, Face Amount										600
Bank of China Jingzhou [Member]
Debt Instrument [Line Items]
Arrangement Fee														$ 100
Time Deposits										$ 900
Debt Instrument, Collateral Amount | ¥																										¥ 6.0

[1] On August 17, 2017, the Company received an interest-free Chinese government loan of RMB 20.0 million, equivalent to approximately $3.0 million, which will mature on August 16, 2018. Henglong pledged RMB 20.0 million, equivalent to approximately $3.0 million, of notes receivable as security for the Chinese government loan (See Note 4). On April 21, 2017, the Company received an interest-free Chinese government loan of RMB 10.0 million, equivalent to approximately $1.5 million, which will mature on December 8, 2017. Jiulong pledged RMB 10.0 million, equivalent to approximately $1.5 million, of notes receivable as security for the Chinese government loan (See Note 4).

[2] On September 26, 2016, Henglong entered into a credit facility agreement with China CITIC Bank to obtain credit facilities in the amount of RMB 170.0 million (equivalent to $25.6 million as of September 30, 2017), the “Henglong CITIC Credit Facility”. The Henglong CITIC Credit Facility expired on September 26, 2017. As security for the Henglong CITIC Credit Facility, Henglong’s property, plant and equipment were pledged and Hubei Henglong provided a guarantee. On March 3, 2017, Henglong drew down loans amounting to RMB 32.5 million, RMB 32.5 million and 30.6 million (equivalent to $4.9 million, $4.9 million and $4.6 million as of September 30, 2017), respectively. The loans will mature on February 5, 6 and 7, 2018, respectively. The annual interest rate of the loans is 4.99%. The principal and interest will be paid at maturity. On September 26, 2016, Hubei Henglong entered into a credit facility agreement with China CITIC Bank to obtain credit facilities in the amount of RMB 100.0 million (equivalent to $15.1 million as of September 30, 2017), the “Hubei Henglong CITIC Credit Facility”. The Hubei Henglong CITIC Credit Facility expired on September 26, 2017. Henglong provided a guarantee for the Hubei Henglong CITIC Credit Facility. On March 3, 2017, Hubei Henglong drew down loans amounting to RMB 28.7 million, RMB 28.7 million and 38.2 million (equivalent to $4.3 million, $4.3 million and $5.8 million), respectively. The loans will mature on February 2, 8 and 9, 2018, respectively. The annual interest rate of the loans is 5.0%. The principal and interest will be paid at maturity.