Loans, Allowance for Loan Losses and Credit Quality (Details 5) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013 loan	Dec. 31, 2012 loan
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	188	310
Principal Balance 30-59 Days	$ 13,767	$ 14,109
Number of Loans 60-89 Days	63	72
Principal Balance 60-89 Days	5,717	5,450
Number of Loans 90 Days or More	162	149
Principal Balance 90 Days or More	21,562	17,295
Number of Loans Total Past Due	413	531
Principal Balance Total Past Due	41,046	36,854
Current	4,514,983	4,482,157
Total Financing Receivables	4,556,029	4,519,011
Recorded Investment >90 Days and Accruing	544	52
Commercial and Industrial [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	7	14
Principal Balance 30-59 Days	837	1,305
Number of Loans 60-89 Days	5	7
Principal Balance 60-89 Days	851	336
Number of Loans 90 Days or More	22	23
Principal Balance 90 Days or More	4,033	1,875
Number of Loans Total Past Due	34	44
Principal Balance Total Past Due	5,721	3,516
Current	750,501	683,995
Total Financing Receivables	756,222	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	17	19
Principal Balance 30-59 Days	8,175	5,028
Number of Loans 60-89 Days	6	8
Principal Balance 60-89 Days	2,150	2,316
Number of Loans 90 Days or More	29	31
Principal Balance 90 Days or More	8,987	6,054
Number of Loans Total Past Due	52	58
Principal Balance Total Past Due	19,312	13,398
Current	2,146,969	2,108,755
Total Financing Receivables	2,166,281	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	100
Number of Loans Total Past Due	1
Principal Balance Total Past Due	100
Current	236,366	188,768
Total Financing Receivables	236,466	188,768
Recorded Investment >90 Days and Accruing
Small Business [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	14	20
Principal Balance 30-59 Days	328	750
Number of Loans 60-89 Days	8	8
Principal Balance 60-89 Days	295	94
Number of Loans 90 Days or More	18	10
Principal Balance 90 Days or More	278	320
Number of Loans Total Past Due	40	38
Principal Balance Total Past Due	901	1,164
Current	74,372	77,430
Total Financing Receivables	75,273	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	17	17
Principal Balance 30-59 Days	2,315	3,053
Number of Loans 60-89 Days	9	7
Principal Balance 60-89 Days	1,679	1,848
Number of Loans 90 Days or More	38	40
Principal Balance 90 Days or More	6,335	7,501
Number of Loans Total Past Due	64	64
Principal Balance Total Past Due	10,329	12,402
Current	486,135	600,479
Total Financing Receivables	496,464	612,881
Recorded Investment >90 Days and Accruing	433
Consumer Home Equity [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	19	32
Principal Balance 30-59 Days	1,558	2,756
Number of Loans 60-89 Days	7	10
Principal Balance 60-89 Days	646	632
Number of Loans 90 Days or More	23	17
Principal Balance 90 Days or More	1,598	1,392
Number of Loans Total Past Due	49	59
Principal Balance Total Past Due	3,802	4,780
Current	800,868	797,369
Total Financing Receivables	804,670	802,149
Recorded Investment >90 Days and Accruing
Consumer - Other [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days	114	208
Principal Balance 30-59 Days	554	1,217
Number of Loans 60-89 Days	28	32
Principal Balance 60-89 Days	96	224
Number of Loans 90 Days or More	31	28
Principal Balance 90 Days or More	231	153
Number of Loans Total Past Due	173	268
Principal Balance Total Past Due	881	1,594
Current	19,772	25,361
Total Financing Receivables	20,653	26,955
Recorded Investment >90 Days and Accruing	$ 111	$ 52