Pledged deposits (Narrative) (Details) - 12 months ended Dec. 31, 2017	USD ($)	CNY (¥)
Pledged Deposits 1 | $	$ 1,295,849
Pledged Deposits 2 | ¥		¥ 8,430,792
Pledged Deposits 3 | $	1,000,000
Pledged Deposits 4 | ¥		6,300,000
Pledged Deposits 5 | $	31,469
Pledged Deposits 6 | ¥		200,000
Pledged Deposits 7 | $	300,000
Pledged Deposits 8 | ¥		1,900,000
Pledged Deposits 9 | $	$ 1,295,849
Pledged Deposits 10 | ¥		¥ 8,430,792