Loans and Allowance for Loan Losses (Details 6) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Activity in allowance for loan losses and recorded investments in loans
Beginning balance	$ 29,689,000	$ 38,720,000	$ 36,532,000	$ 45,368,000
Provision for loan losses	(400,000)	1,100,000	(3,400,000)	5,000,000
Charge-offs	(1,891,000)	(1,342,000)	(11,175,000)	(14,106,000)
Recoveries	364,000	873,000	5,805,000	3,089,000
Ending balance	27,762,000	39,351,000	27,762,000	39,351,000
Ending balance: individually evaluated for impairment	15,803,000	9,124,000	15,803,000	9,124,000
Ending balance: collectively evaluated for impairment	11,959,000	30,227,000	11,959,000	30,227,000
Ending balance	1,035,288,000	1,094,037,000	1,035,288,000	1,094,037,000	1,072,422,000
Ending balance: individually evaluated for impairment	63,214,000	50,403,000	63,214,000	50,403,000
Ending balance: collectively evaluated for impairment	972,074,000	1,043,634,000	972,074,000	1,043,634,000
Commercial Loans [Member]
Activity in allowance for loan losses and recorded investments in loans
Beginning balance	26,471,000	35,986,000	33,431,000	42,358,000
Provision for loan losses	(355,000)	586,000	(3,480,000)	3,074,000
Charge-offs	(1,548,000)	(1,260,000)	(10,662,000)	(12,168,000)
Recoveries	326,000	838,000	5,605,000	2,886,000
Ending balance	24,894,000	36,150,000	24,894,000	36,150,000
Ending balance: individually evaluated for impairment	15,498,000	8,543,000	15,498,000	8,543,000
Ending balance: collectively evaluated for impairment	9,396,000	27,607,000	9,396,000	27,607,000
Ending balance	957,411,000	1,012,973,000	957,411,000	1,012,973,000	996,905,000
Ending balance: individually evaluated for impairment	61,378,000	47,556,000	61,378,000	47,556,000
Ending balance: collectively evaluated for impairment	896,033,000	965,417,000	896,033,000	965,417,000
Retail Loans [Member]
Activity in allowance for loan losses and recorded investments in loans
Beginning balance	3,167,000	2,641,000	3,019,000	2,972,000
Provision for loan losses	(35,000)	533,000	121,000	1,890,000
Charge-offs	(343,000)	(82,000)	(513,000)	(1,938,000)
Recoveries	38,000	35,000	200,000	203,000
Ending balance	2,827,000	3,127,000	2,827,000	3,127,000
Ending balance: individually evaluated for impairment	305,000	581,000	305,000	581,000
Ending balance: collectively evaluated for impairment	2,522,000	2,546,000	2,522,000	2,546,000
Ending balance	77,877,000	81,064,000	77,877,000	81,064,000	75,517,000
Ending balance: individually evaluated for impairment	1,836,000	2,847,000	1,836,000	2,847,000
Ending balance: collectively evaluated for impairment	76,041,000	78,217,000	76,041,000	78,217,000
Unallocated [Member]
Activity in allowance for loan losses and recorded investments in loans
Beginning balance	51,000	93,000	82,000	38,000
Provision for loan losses	(10,000)	(19,000)	(41,000)	36,000
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Ending balance	41,000	74,000	41,000	74,000
Ending balance: individually evaluated for impairment	0	0	0	0
Ending balance: collectively evaluated for impairment	41,000	74,000	41,000	74,000
Ending balance
Ending balance: individually evaluated for impairment
Ending balance: collectively evaluated for impairment