Loans Receivable and Allowance for Loan Losses (Summary of Allowances on Loans Receivable, by Class) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	$ 23,759	$ 21,850	$ 21,620	$ 21,618
Provision charged to operating expenses	2,950	1,700	5,450	3,492
Recoveries of loans previously charged-off	247	78	734	124
Loans charged-off	(798)	(1,905)	(1,646)	(3,511)
Allowance for loan losses, ending	26,158	21,723	26,158	21,723
Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	8,251	8,861	8,400	9,679
Provision charged to operating expenses	2,481	734	2,434	132
Recoveries of loans previously charged-off	180	15	201	53
Loans charged-off	(337)	(659)	(460)	(913)
Allowance for loan losses, ending	10,575	8,951	10,575	8,951
Commercial tax-exempt [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	72	83	79	86
Provision charged to operating expenses	2	(2)	(5)	(5)
Recoveries of loans previously charged-off	0	0	0	0
Loans charged-off	0	0	0	0
Allowance for loan losses, ending	74	81	74	81
Owner occupied real estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	1,794	942	729	910
Provision charged to operating expenses	368	52	1,473	86
Recoveries of loans previously charged-off	4	0	7	0
Loans charged-off	(49)	0	(92)	(2)
Allowance for loan losses, ending	2,117	994	2,117	994
Commercial construction and land development [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	8,940	6,016	7,840	5,420
Provision charged to operating expenses	172	375	1,225	1,353
Recoveries of loans previously charged-off	15	0	450	0
Loans charged-off	(210)	(1,000)	(598)	(1,382)
Allowance for loan losses, ending	8,917	5,391	8,917	5,391
Commercial real estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	3,347	4,583	3,241	4,002
Provision charged to operating expenses	(129)	492	140	1,503
Recoveries of loans previously charged-off	27	2	30	8
Loans charged-off	(106)	(42)	(272)	(478)
Allowance for loan losses, ending	3,139	5,035	3,139	5,035
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	426	461	435	442
Provision charged to operating expenses	22	(52)	67	68
Recoveries of loans previously charged-off	0	29	1	29
Loans charged-off	(10)	0	(65)	(101)
Allowance for loan losses, ending	438	438	438	438
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	783	761	831	702
Provision charged to operating expenses	79	184	80	672
Recoveries of loans previously charged-off	21	32	45	34
Loans charged-off	(86)	(204)	(159)	(635)
Allowance for loan losses, ending	797	773	797	773
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	146	143	65	377
Provision charged to operating expenses	(45)	(83)	36	(317)
Recoveries of loans previously charged-off	0	0	0	0
Loans charged-off	0	0	0	0
Allowance for loan losses, ending	$ 101	$ 60	$ 101	$ 60