Loans Receivable and Allowance for Loan Losses (Age Analysis of Past Due Loan Receivables) (Details) (USD $)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Current	$ 1,587,929,000		$ 1,487,781,000
30-59 Days Past Due	8,922,000		16,383,000
60-89 Days Past Due	12,631,000		9,667,000
90 Days Past Due and Greater	24,384,000		14,966,000
Total Past Due	45,937,000		41,016,000
Total loans receivable	1,633,866,000		1,528,797,000
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		220,000
Transfer of loans to foreclosed assets	2,693,000	1,421,000
Loan receivables, transitioned from current to past-due	22,331,000		19,111,000
Reserve for loan receivables	10,335,000		7,120,000
Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	402,836,000		368,769,000
30-59 Days Past Due	5,307,000		1,096,000
60-89 Days Past Due	3,067,000		3,256,000
90 Days Past Due and Greater	4,530,000		3,867,000
Total Past Due	12,904,000		8,219,000
Total loans receivable	415,740,000		376,988,000
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		30,000
Loan receivables, transitioned from current to past-due	5,305,000		5,656,000
Reserve for loan receivables	2,695,000		2,399,000
Number of loan receivable agreements	2
Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	82,455,000		92,202,000
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	82,455,000		92,202,000
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		0
Reserve for loan receivables	0		0
Owner occupied real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	283,912,000		265,817,000
30-59 Days Past Due	998,000		610,000
60-89 Days Past Due	626,000		353,000
90 Days Past Due and Greater	3,166,000		1,592,000
Total Past Due	4,790,000		2,555,000
Total loans receivable	288,702,000		268,372,000
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		0
Loan receivables, transitioned from current to past-due	1,415,000		1,451,000
Reserve for loan receivables	1,415,000		1,451,000
Increase (decrease) in recorded investment, past due	2,200,000
Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	97,258,000		89,250,000
30-59 Days Past Due	0		4,251,000
60-89 Days Past Due	0		4,318,000
90 Days Past Due and Greater	8,338,000		2,580,000
Total Past Due	8,338,000		11,149,000
Total loans receivable	105,596,000		100,399,000
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		188,000
Loan receivables, transitioned from current to past-due	7,809,000		7,833,000
Reserve for loan receivables	3,470,000		2,470,000
Increase (decrease) in recorded investment, past due	(2,800,000)
Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	427,131,000		386,821,000
30-59 Days Past Due	822,000		3,846,000
60-89 Days Past Due	4,889,000		78,000
90 Days Past Due and Greater	786,000		3,659,000
Total Past Due	6,497,000		7,583,000
Total loans receivable	433,628,000		394,404,000
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		0
Loan receivables, transitioned from current to past-due	4,157,000		4,171,000
Reserve for loan receivables	1,755,000		800,000
Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	82,560,000		76,587,000
30-59 Days Past Due	0		4,303,000
60-89 Days Past Due	2,258,000		1,252,000
90 Days Past Due and Greater	5,772,000		1,757,000
Total Past Due	8,030,000		7,312,000
Total loans receivable	90,590,000		83,899,000
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		0
Loan receivables, transitioned from current to past-due	3,153,000		0
Reserve for loan receivables	508,000		0
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	211,777,000		208,335,000
30-59 Days Past Due	1,795,000		2,277,000
60-89 Days Past Due	1,791,000		410,000
90 Days Past Due and Greater	1,792,000		1,511,000
Total Past Due	5,378,000		4,198,000
Total loans receivable	217,155,000		212,533,000
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		2,000
Loan receivables, transitioned from current to past-due	492,000		0
Reserve for loan receivables	492,000		0
Improvement to Current Status [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	13,000,000
Paid Off During the Quarter [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	4,100,000
Current at Previous Fiscal Year End [Member]
Financing Receivable, Recorded Investment [Line Items]
30-59 Days Past Due	8,200,000
60-89 Days Past Due	14,100,000
90 Days Past Due and Greater	3,500,000
Total Past Due	25,800,000
Charged Off [Member]
Financing Receivable, Recorded Investment [Line Items]
Write-off of financing receivable	999,000
Transition to Foreclosed Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Transfer of loans to foreclosed assets	$ 2,600,000