Loans Receivable and Allowance for Loan Losses (Age Analysis of Past Due Loan Receivables) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012 Relationships	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Current	$ 1,454,330	$ 1,397,758
30-59 Days Past Due	4,285	11,681
60-89 Days Past Due	13,423	3,859
90 Days Past Due and Greater	20,717	23,370
Total Past Due	38,425	38,910
Total loans receivable	1,492,755	1,436,668
Recorded Investment in Loans 90 Days and Greater and Still Accruing	154	692
Number of Large Receivable Relationships	3
Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	345,367	317,016
30-59 Days Past Due	413	696
60-89 Days Past Due	3,966	1,083
90 Days Past Due and Greater	6,997	3,193
Total Past Due	11,376	4,972
Total loans receivable	356,743	321,988
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	0
Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	84,616	81,532
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	84,616	81,532
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	269,395	274,720
30-59 Days Past Due	557	2,423
60-89 Days Past Due	1,380	328
90 Days Past Due and Greater	3,172	1,901
Total Past Due	5,109	4,652
Total loans receivable	274,504	279,372
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	0
Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	103,699	94,160
30-59 Days Past Due	222	470
60-89 Days Past Due	492	219
90 Days Past Due and Greater	3,606	8,304
Total Past Due	4,320	8,993
Total loans receivable	108,019	103,153
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	0
Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	364,765	354,818
30-59 Days Past Due	2,107	2,191
60-89 Days Past Due	6,493	1,272
90 Days Past Due and Greater	3,883	6,124
Total Past Due	12,483	9,587
Total loans receivable	377,248	364,405
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	0
Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	81,517	75,841
30-59 Days Past Due	181	4,587
60-89 Days Past Due	697	607
90 Days Past Due and Greater	1,985	2,905
Total Past Due	2,863	8,099
Total loans receivable	84,380	83,940
Recorded Investment in Loans 90 Days and Greater and Still Accruing	154	621
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	204,971	199,671
30-59 Days Past Due	805	1,314
60-89 Days Past Due	395	350
90 Days Past Due and Greater	1,074	943
Total Past Due	2,274	2,607
Total loans receivable	207,245	202,278
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0	71
Improvement to Current Status [Member]
Financing Receivable, Recorded Investment [Line Items]
30-59 Days Past Due		1,000
90 Days Past Due and Greater		1,100
Collections [Member]
Financing Receivable, Recorded Investment [Line Items]
30-59 Days Past Due		1,000
Normal Fluctuations [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
30-59 Days Past Due		3,700
Transition to 60 - 89 Category [Member]
Financing Receivable, Recorded Investment [Line Items]
30-59 Days Past Due		1,000
Number of Large Receivable Relationships	1
Current at Previous Fiscal Year End [Member]
Financing Receivable, Recorded Investment [Line Items]
60-89 Days Past Due		8,300
Improvement to 60 - 89 Category [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of Large Receivable Relationships	1
Nonaccrual Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
60-89 Days Past Due		$ 3,400
Number of Large Receivable Relationships	1