Borrowings (Schedule of Short-Term Loans, Including Current Portion of Long-Term Bank Loans) (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Short-term Debt [Line Items]
Total short-term loans, including current portion of long-term bank loans	$ 723,302,348	$ 729,666,920
Unsecured loans [Member]
Short-term Debt [Line Items]
Total short-term loans, including current portion of long-term bank loans	394,064,008	411,469,868
Loans secured by accounts receivable [Member]
Short-term Debt [Line Items]
Total short-term loans, including current portion of long-term bank loans	66,830,029	65,567,082
Loans secured by restricted cash [Member]
Short-term Debt [Line Items]
Total short-term loans, including current portion of long-term bank loans	84,351,118	69,500,000
Current portion of long-term bank loans [Member]
Short-term Debt [Line Items]
Total short-term loans, including current portion of long-term bank loans	$ 178,057,193	$ 176,401,330