Loans and reserve for credit losses (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Balance at beginning of year	$ 43,905	$ 46,668	$ 58,586
Loan loss provision (credit)	1,100	75,000	24,000
Recoveries	4,449	3,592	9,112
Loans charged off	(22,193)		(45,030)
Loans charged-off in the normal course of business		(27,287)
Loans charged-off as a result of the Bulk Sale (see Note 2)		(54,068)
Balance at end of period	27,261	43,905	46,668
Reserve for unfunded loan commitments
Balance at beginning of year	1,550	941	704
Provision (credit) for unfunded loan commitments	(1,110)	609	237
Balance at end of year	440	1,550	941
Reserve for credit losses
Reserve for loan losses	27,261	43,905	46,668
Reserve for unfunded lending commitments	440	1,550	941
Total reserve for credit losses	27,701	45,455	47,609
Commerical real estate [Member]
Balance at beginning of year	21,648	14,338
Loan loss provision (credit)	2,829	29,908
Recoveries	198	119
Loans charged off	(13,079)
Loans charged-off in the normal course of business		(3,501)
Loans charged-off as a result of the Bulk Sale (see Note 2)		(19,216)
Balance at end of period	11,596	21,648
Reserve for unfunded loan commitments
Balance at beginning of year	28	40
Provision (credit) for unfunded loan commitments	20	(12)
Balance at end of year	48	28
Reserve for credit losses
Reserve for loan losses	11,596	21,648
Reserve for unfunded lending commitments	48	28
Total reserve for credit losses	11,644	21,676
Construction [Member]
Balance at beginning of year	5,398	12,652
Loan loss provision (credit)	(4,135)	22,019
Recoveries	584	1,551
Loans charged off	(264)
Loans charged-off in the normal course of business		(5,536)
Loans charged-off as a result of the Bulk Sale (see Note 2)		(25,288)
Balance at end of period	1,583	5,398
Reserve for unfunded loan commitments
Balance at beginning of year	29	0
Provision (credit) for unfunded loan commitments	239	29
Balance at end of year	268	29
Reserve for credit losses
Reserve for loan losses	1,583	5,398
Reserve for unfunded lending commitments	268	29
Total reserve for credit losses	1,851	5,427
Residential real estate [Member]
Balance at beginning of year	3,259	4,116
Loan loss provision (credit)	2,650	4,196
Recoveries	262	164
Loans charged off	(2,620)
Loans charged-off in the normal course of business		(2,238)
Loans charged-off as a result of the Bulk Sale (see Note 2)		(2,979)
Balance at end of period	3,551	3,259
Reserve for unfunded loan commitments
Balance at beginning of year	184	101
Provision (credit) for unfunded loan commitments	(159)	83
Balance at end of year	25	184
Reserve for credit losses
Reserve for loan losses	3,551	3,259
Reserve for unfunded lending commitments	25	184
Total reserve for credit losses	3,576	3,443
Commercial and industrial [Member]
Balance at beginning of year	11,291	12,220
Loan loss provision (credit)	(2,094)	17,724
Recoveries	3,094	1,453
Loans charged off	(5,024)
Loans charged-off in the normal course of business		(13,626)
Loans charged-off as a result of the Bulk Sale (see Note 2)		(6,480)
Balance at end of period	7,267	11,291
Reserve for unfunded loan commitments
Balance at beginning of year	487	523
Provision (credit) for unfunded loan commitments	(412)	(36)
Balance at end of year	75	487
Reserve for credit losses
Reserve for loan losses	7,267	11,291
Reserve for unfunded lending commitments	75	487
Total reserve for credit losses	7,342	11,778
Consumer Loans [Member]
Balance at beginning of year	2,292	2,966
Loan loss provision (credit)	780	1,512
Recoveries	311	305
Loans charged off	(1,206)
Loans charged-off in the normal course of business		(2,386)
Loans charged-off as a result of the Bulk Sale (see Note 2)		(105)
Balance at end of period	2,177	2,292
Reserve for unfunded loan commitments
Balance at beginning of year	822	241
Provision (credit) for unfunded loan commitments	(798)	581
Balance at end of year	24	822
Reserve for credit losses
Reserve for loan losses	2,177	2,292
Reserve for unfunded lending commitments	24	822
Total reserve for credit losses	2,201	3,114
Unallocated [Member]
Balance at beginning of year	17	377
Loan loss provision (credit)	1,070	(359)
Recoveries	0	0
Loans charged off	0
Loans charged-off in the normal course of business		0
Loans charged-off as a result of the Bulk Sale (see Note 2)		0
Balance at end of period	1,087	17
Reserve for unfunded loan commitments
Balance at beginning of year	0	36
Provision (credit) for unfunded loan commitments	0	(36)
Balance at end of year	0	0
Reserve for credit losses
Reserve for loan losses	1,087	17
Reserve for unfunded lending commitments	0	0
Total reserve for credit losses	$ 1,087	$ 18