Loans, Allowance for Loan Losses and Credit Quality (Details 5) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013 loan	Dec. 31, 2012 loan
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	234	310
Principal Balance 30-59 Days	$ 12,162	$ 14,109
Number of Loans 60-89 Days	64	72
Principal Balance 60-89 Days	14,532	5,450
Number of Loans 90 Days or More	152	149
Principal Balance 90 Days or More	20,074	17,295
Number of Loans Total Past Due	450	531
Principal Balance Total Past Due	46,768	36,854
Current	4,483,343	4,482,157
Total Financing Receivables	4,530,111	4,519,011
Recorded Investment >90 Days and Accruing	54	52
Commercial and Industrial [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	15	14
Principal Balance 30-59 Days	1,481	1,305
Number of Loans 60-89 Days	13	7
Principal Balance 60-89 Days	1,821	336
Number of Loans 90 Days or More	22	23
Principal Balance 90 Days or More	2,407	1,875
Number of Loans Total Past Due	50	44
Principal Balance Total Past Due	5,709	3,516
Current	736,634	683,995
Total Financing Receivables	742,343	687,511
Recorded Investment >90 Days and Accruing
Commercial Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	51	19
Principal Balance 30-59 Days	5,454	5,028
Number of Loans 60-89 Days	10	8
Principal Balance 60-89 Days	9,581	2,316
Number of Loans 90 Days or More	27	31
Principal Balance 90 Days or More	6,529	6,054
Number of Loans Total Past Due	88	58
Principal Balance Total Past Due	21,564	13,398
Current	2,129,269	2,108,755
Total Financing Receivables	2,150,833	2,122,153
Recorded Investment >90 Days and Accruing
Commercial Construction [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days
Principal Balance 30-59 Days
Number of Loans 60-89 Days
Principal Balance 60-89 Days
Number of Loans 90 Days or More	1
Principal Balance 90 Days or More	1,608
Number of Loans Total Past Due	1
Principal Balance Total Past Due	1,608
Current	230,111	188,768
Total Financing Receivables	231,719	188,768
Recorded Investment >90 Days and Accruing
Small Business [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	25	20
Principal Balance 30-59 Days	717	750
Number of Loans 60-89 Days	11	8
Principal Balance 60-89 Days	149	94
Number of Loans 90 Days or More	13	10
Principal Balance 90 Days or More	359	320
Number of Loans Total Past Due	49	38
Principal Balance Total Past Due	1,225	1,164
Current	76,058	77,430
Total Financing Receivables	77,283	78,594
Recorded Investment >90 Days and Accruing
Residential Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	15	17
Principal Balance 30-59 Days	3,359	3,053
Number of Loans 60-89 Days	4	7
Principal Balance 60-89 Days	1,768	1,848
Number of Loans 90 Days or More	38	40
Principal Balance 90 Days or More	6,982	7,501
Number of Loans Total Past Due	57	64
Principal Balance Total Past Due	12,109	12,402
Current	501,442	600,479
Total Financing Receivables	513,551	612,881
Recorded Investment >90 Days and Accruing
Consumer Home Equity [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	16	32
Principal Balance 30-59 Days	592	2,756
Number of Loans 60-89 Days	12	10
Principal Balance 60-89 Days	1,174	632
Number of Loans 90 Days or More	23	17
Principal Balance 90 Days or More	2,009	1,392
Number of Loans Total Past Due	51	59
Principal Balance Total Past Due	3,775	4,780
Current	788,675	797,369
Total Financing Receivables	792,450	802,149
Recorded Investment >90 Days and Accruing
Consumer - Other [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	112	208
Principal Balance 30-59 Days	559	1,217
Number of Loans 60-89 Days	14	32
Principal Balance 60-89 Days	39	224
Number of Loans 90 Days or More	28	28
Principal Balance 90 Days or More	180	153
Number of Loans Total Past Due	154	268
Principal Balance Total Past Due	778	1,594
Current	21,154	25,361
Total Financing Receivables	21,932	26,955
Recorded Investment >90 Days and Accruing	$ 54	$ 52