Other non-current liabilities (Details) - USD ($)		Mar. 31, 2019	Dec. 31, 2018
Other Liabilities, Noncurrent [Abstract]
Income tax payable-noncurrent	[1]	$ 95,285,414	$ 92,461,068
Deferred income tax liabilities		6,312,385	6,716,921
Others		2,395,783	2,395,783
Total other non-current liabilities		$ 103,993,582	$ 101,573,772

[1] Income tax payable-noncurrent represents the repatriation tax, the accumulative balance of unrecognized tax benefits since 2013 and related accrued interest. According to the Tax Cuts and Jobs Act enacted on December 22, 2017, the management recognized the amount of U.S. tax corporate income tax is US$70,965,148 based on the deemed repatriation to the United States of accumulated earnings mandated by the U.S. tax reform, US$17,031,636 of which due payable in 2018 and 2019 was classified as current liabilities.