Segment information (Details Textual) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segment information (Textual) [Abstract]
Taxable Equivalent Adjustment	$ 6,546,000	$ 5,865,000	$ 19,341,000	$ 17,893,000