Disclosure of Major Customers (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 item	Dec. 31, 2011 item	Dec. 31, 2010 item
Disclosure of Major Customers
Number of customers who accounted for more than 10% of revenues	4	4	4
Sunoco, Inc.
Disclosure of Major Customers
Revenue from customers	34,147,610	22,579,414	10,951,458
Valero Marketing & Supply Co.
Disclosure of Major Customers
Revenue from customers	22,321,999
DCP Midstream, LP
Disclosure of Major Customers
Revenue from customers	15,412,128	31,727,341	23,224,023
Shell Trading (U.S.) Company
Disclosure of Major Customers
Revenue from customers	11,692,738