Loans Receivable and Allowance for Loan Losses (Age Analysis of Past Due Loan Receivables) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Current	$ 1,746,871		$ 1,701,797
30-59 Days Past Due	22,000		16,234
60-89 Days Past Due	11,523		11,140
90 Days Past Due and Greater	21,851		21,701
Total Past Due	55,374		49,075
Total loans receivable	1,802,245		1,750,872
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		369
Transfer of loans to foreclosed assets	373	612
Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	457,140		438,522
30-59 Days Past Due	2,948		1,830
60-89 Days Past Due	1,620		1,041
90 Days Past Due and Greater	4,223		5,751
Total Past Due	8,791		8,622
Total loans receivable	465,931		447,144
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		17
Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	77,566		81,734
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	77,566		81,734
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	292,866		295,278
30-59 Days Past Due	2,084		2,618
60-89 Days Past Due	7,579		1,674
90 Days Past Due and Greater	4,236		2,847
Total Past Due	13,899		7,139
Total loans receivable	306,765		302,417
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	115,941		124,240
30-59 Days Past Due	280		3,355
60-89 Days Past Due	147		342
90 Days Past Due and Greater	7,421		5,239
Total Past Due	7,848		8,936
Total loans receivable	123,789		133,176
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		0
Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	503,464		465,765
30-59 Days Past Due	4,491		2,142
60-89 Days Past Due	907		444
90 Days Past Due and Greater	3,720		4,837
Total Past Due	9,118		7,423
Total loans receivable	512,582		473,188
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		235
Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	87,665		85,352
30-59 Days Past Due	10,129		4,194
60-89 Days Past Due	192		6,304
90 Days Past Due and Greater	841		1,916
Total Past Due	11,162		12,414
Total loans receivable	98,827		97,766
Recorded Investment in Loans 90 Days and Greater and Still Accruing	0		117
Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Current	212,229		210,906
30-59 Days Past Due	2,068		2,095
60-89 Days Past Due	1,078		1,335
90 Days Past Due and Greater	1,410		1,111
Total Past Due	4,556		4,541
Total loans receivable	216,785		215,447
Recorded Investment in Loans 90 Days and Greater and Still Accruing	$ 0		$ 0