Allowance for Loan Losses (Details 1) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Ending Balance Attributable to Loans
Individually evaluated for impairment	$ 6,057		$ 7,373
Collectively evaluated for impairment	15,051		14,337
Acquired with deteriorated credit quality	1,025		248
Ending Balance	22,133	25,272	21,958	20,092	18,313	19,242
Loans
Individually evaluated for impairment	25,465		30,694
Collectively evaluated for impairment	1,768,057		1,814,229
Acquired with deteriorated credit quality	14,684		17,009
Ending Balance	1,808,206		1,861,932
Commercial
Ending Balance Attributable to Loans
Individually evaluated for impairment	6,057		3,453
Collectively evaluated for impairment	7,763		7,286
Acquired with deteriorated credit quality	711		248
Ending Balance	14,531	14,144	10,987	13,190	11,448	12,119
Loans
Individually evaluated for impairment	25,201		23,721
Collectively evaluated for impairment	1,014,924		1,056,861
Acquired with deteriorated credit quality	11,513		13,582
Ending Balance	1,051,638		1,094,164
Residential
Ending Balance Attributable to Loans
Individually evaluated for impairment	0		3,920
Collectively evaluated for impairment	1,278		1,506
Acquired with deteriorated credit quality	314		0
Ending Balance	1,592	5,400	5,426	2,124	2,092	2,728
Loans
Individually evaluated for impairment	264		6,973
Collectively evaluated for impairment	484,192		487,486
Acquired with deteriorated credit quality	3,170		3,421
Ending Balance	487,626		497,880
Consumer
Ending Balance Attributable to Loans
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	3,637		3,879
Acquired with deteriorated credit quality	0		0
Ending Balance	3,637	3,481	3,879	3,744	3,806	3,889
Loans
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	268,941		269,882
Acquired with deteriorated credit quality	1		6
Ending Balance	268,942		269,888
Unallocated
Ending Balance Attributable to Loans
Individually evaluated for impairment	0		0
Collectively evaluated for impairment	2,373		1,666
Acquired with deteriorated credit quality	0		0
Ending Balance	$ 2,373	$ 2,247	$ 1,666	$ 1,034	$ 967	$ 506