Cash and cash equivalents and restricted cash (Details Textual) (USD $)	1 Months Ended
	Apr. 30, 2012	Dec. 31, 2011
Restricted Cash and Cash Equivalents		$ 7,500,000
Deposits Pledged As Collateral		7,500,000
Line Of Credit Facility, Paid Off Amount	7,500,000
Line of Credit Facility, Amount Outstanding	$ 10,000,000