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, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	$ 27,472	$ 23,759	$ 25,282	$ 21,620
Provision charged to operating expenses	1,800	2,950	4,100	5,450
Recoveries of loans previously charged-off	228	247	894	734
Loans charged-off	(1,462)	(798)	(2,238)	(1,646)
Allowance for loan losses, ending	28,038	26,158	28,038	26,158
Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	10,408	8,251	9,959	8,400
Provision charged to operating expenses	1,175	2,481	1,522	2,434
Recoveries of loans previously charged-off	194	180	332	201
Loans charged-off	(1,228)	(337)	(1,264)	(460)
Allowance for loan losses, ending	10,549	10,575	10,549	10,575
Commercial tax-exempt [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	75	72	83	79
Provision charged to operating expenses	(1)	2	(9)	(5)
Recoveries of loans previously charged-off	0	0	0	0
Loans charged-off	0	0	0	0
Allowance for loan losses, ending	74	74	74	74
Owner occupied real estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	2,208	1,794	2,129	729
Provision charged to operating expenses	51	368	311	1,473
Recoveries of loans previously charged-off	0	4	3	7
Loans charged-off	(52)	(49)	(236)	(92)
Allowance for loan losses, ending	2,207	2,117	2,207	2,117
Commercial construction and land development [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	7,967	8,940	7,222	7,840
Provision charged to operating expenses	(161)	172	115	1,225
Recoveries of loans previously charged-off	12	15	498	450
Loans charged-off	(8)	(210)	(25)	(598)
Allowance for loan losses, ending	7,810	8,917	7,810	8,917
Commercial real estate [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	5,038	3,347	3,983	3,241
Provision charged to operating expenses	162	(129)	1,299	140
Recoveries of loans previously charged-off	0	27	0	30
Loans charged-off	(141)	(106)	(223)	(272)
Allowance for loan losses, ending	5,059	3,139	5,059	3,139
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	338	426	324	435
Provision charged to operating expenses	539	22	666	67
Recoveries of loans previously charged-off	0	0	3	1
Loans charged-off	(14)	(10)	(130)	(65)
Allowance for loan losses, ending	863	438	863	438
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	787	783	793	831
Provision charged to operating expenses	468	79	767	80
Recoveries of loans previously charged-off	22	21	58	45
Loans charged-off	(19)	(86)	(360)	(159)
Allowance for loan losses, ending	1,258	797	1,258	797
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning	651	146	789	65
Provision charged to operating expenses	(433)	(45)	(571)	36
Recoveries of loans previously charged-off	0	0	0	0
Loans charged-off	0	0	0	0
Allowance for loan losses, ending	$ 218	$ 101	$ 218	$ 101