XML 71 R62.htm IDEA: XBRL DOCUMENT v3.19.1
Commitments and contingencies - Operating Leases (Details)
Dec. 31, 2018
USD ($)
Commitments and Contingencies Disclosure [Abstract]  
Within one year $ 1,802,872
One to two years 1,882,422
Two to three years 1,962,242
Three to four years 2,042,062
Four to five years 2,121,882
Five years and thereafter 8,001,955
Total $ 17,813,435