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		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	$ 26,158	$ 21,723	$ 21,620	$ 21,618
Provision charged to operating expenses	2,500	13,750	7,950	17,242
Recoveries of loans previously charged-off	157	43	891	167
Loans charged-off	(3,219)	(12,209)	(4,865)	(15,720)
Allowance for loan losses, ending	25,596	23,307	25,596	23,307
Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	10,575	8,951	8,400	9,679
Provision charged to operating expenses	398	4,841	2,832	4,973
Recoveries of loans previously charged-off	15	21	216	74
Loans charged-off	(487)	(3,909)	(947)	(4,822)
Allowance for loan losses, ending	10,501	9,904	10,501	9,904
Commercial tax-exempt [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	74	81	79	86
Provision charged to operating expenses	6	(3)	1	(8)
Recoveries of loans previously charged-off	0	0	0	0
Loans charged-off	0	0	0	0
Allowance for loan losses, ending	80	78	80	78
Owner occupied real estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	2,117	994	729	910
Provision charged to operating expenses	294	(58)	1,766	28
Recoveries of loans previously charged-off	0	1	8	1
Loans charged-off	0	(252)	(92)	(254)
Allowance for loan losses, ending	2,411	685	2,411	685
Commercial construction and land development [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	8,917	5,391	7,840	5,420
Provision charged to operating expenses	(762)	8,781	464	10,134
Recoveries of loans previously charged-off	64	0	513	0
Loans charged-off	(625)	(7,532)	(1,223)	(8,914)
Allowance for loan losses, ending	7,594	6,640	7,594	6,640
Commercial real estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	3,139	5,035	3,241	4,002
Provision charged to operating expenses	1,609	(119)	1,749	1,384
Recoveries of loans previously charged-off	55	2	85	10
Loans charged-off	(1,580)	(199)	(1,852)	(677)
Allowance for loan losses, ending	3,223	4,719	3,223	4,719
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	438	438	435	442
Provision charged to operating expenses	101	16	168	84
Recoveries of loans previously charged-off	3	0	4	29
Loans charged-off	(198)	(46)	(263)	(147)
Allowance for loan losses, ending	344	408	344	408
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	797	773	831	702
Provision charged to operating expenses	301	302	381	974
Recoveries of loans previously charged-off	20	19	65	53
Loans charged-off	(329)	(271)	(488)	(906)
Allowance for loan losses, ending	789	823	789	823
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	101	60	65	377
Provision charged to operating expenses	553	(10)	589	(327)
Recoveries of loans previously charged-off	0	0	0	0
Loans charged-off	0	0	0	0
Allowance for loan losses, ending	$ 654	$ 50	$ 654	$ 50