Loans Receivable and Allowance for Loan Losses (Age Analysis of Past Due Loan Receivables) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Current	$ 1,960,032	$ 1,963,906
30-59 Days Past Due	19,607	11,612
60-89 Days Past Due	8,076	6,144
90 Days Past Due and Greater	15,995	16,872
Total Past Due	43,678	34,628
Total loans receivable	2,003,710	1,998,534
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	445
Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	527,272	514,428
30-59 Days Past Due	2,897	1,574
60-89 Days Past Due	1,212	3,398
90 Days Past Due and Greater	4,968	5,727
Total Past Due	9,077	10,699
Total loans receivable	536,349	525,127
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	0
Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	67,176	71,151
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
90 Days Past Due and Greater	0	0
Total Past Due	0	0
Total loans receivable	67,176	71,151
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	0
Owner occupied real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	299,018	325,681
30-59 Days Past Due	2,504	606
60-89 Days Past Due	5,024	44
90 Days Past Due and Greater	4,713	5,739
Total Past Due	12,241	6,389
Total loans receivable	311,259	332,070
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	445
Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	136,468	137,263
30-59 Days Past Due	236	611
60-89 Days Past Due	328	190
90 Days Past Due and Greater	31	0
Total Past Due	595	801
Total loans receivable	137,063	138,064
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	0
Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	600,420	591,383
30-59 Days Past Due	3,463	1,104
60-89 Days Past Due	1,160	175
90 Days Past Due and Greater	2,357	1,614
Total Past Due	6,980	2,893
Total loans receivable	607,400	594,276
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	0
Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	106,939	101,233
30-59 Days Past Due	6,410	5,067
60-89 Days Past Due	151	1,900
90 Days Past Due and Greater	2,643	2,751
Total Past Due	9,204	9,718
Total loans receivable	116,143	110,951
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	0
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	222,739	222,767
30-59 Days Past Due	4,097	2,650
60-89 Days Past Due	201	437
90 Days Past Due and Greater	1,283	1,041
Total Past Due	5,581	4,128
Total loans receivable	228,320	226,895
Recorded Investment in Loans 90 Days and Greater and Still Accruing	$ 0	$ 0