Commitments and contingencies (Details Textual) ¥ in Millions, $ in Millions	Jun. 30, 2015 USD ($)	Jun. 30, 2015 CNY (¥)	Apr. 24, 2015 USD ($)	Apr. 24, 2015 CNY (¥)	Oct. 20, 2014 USD ($)	Oct. 20, 2014 CNY (¥)	Sep. 22, 2014 USD ($)	Sep. 22, 2014 CNY (¥)
Commitments and Contingencies Disclosure [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent							17.90%	17.90%
Hubei Henglong [Member]
Commitments and Contingencies Disclosure [Line Items]
Capital			$ 1.6	¥ 10.0	$ 0.8	¥ 5.0	$ 8.1	¥ 50.0
Suzhou Qingyan Automobile Industry Venture Firm [Member]
Commitments and Contingencies Disclosure [Line Items]
Unpaid Capital	$ 5.7	¥ 35.0