Loans Receivable and Allowance for Loan Losses (Credit Quality Indicators for Commercial Loans, by Loan Type) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	$ 1,326,121	$ 1,232,365
Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	415,740	376,988
Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	82,455	92,202
Owner occupied real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	288,702	268,372
Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	105,596	100,399
Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	433,628	394,404
Pass Rated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	1,231,893	1,141,535
Pass Rated Loans [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	367,438	335,463
Pass Rated Loans [Member] | Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	82,455	92,202
Pass Rated Loans [Member] | Owner occupied real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	272,441	253,338
Pass Rated Loans [Member] | Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	89,173	81,219
Pass Rated Loans [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	420,386	379,313
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	17,906	15,900
Special Mention [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	11,646	6,120
Special Mention [Member] | Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	0	0
Special Mention [Member] | Owner occupied real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	3,842	4,160
Special Mention [Member] | Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	1,851	5,046
Special Mention [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	567	574
Substandard Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	43,350	48,563
Substandard Accrual [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	24,603	24,116
Substandard Accrual [Member] | Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	0	0
Substandard Accrual [Member] | Owner occupied real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	7,420	7,755
Substandard Accrual [Member] | Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	2,545	7,834
Substandard Accrual [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	8,782	8,858
Substandard Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	32,972	26,367
Substandard Nonaccrual [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	12,053	11,289
Substandard Nonaccrual [Member] | Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	0	0
Substandard Nonaccrual [Member] | Owner occupied real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	4,999	3,119
Substandard Nonaccrual [Member] | Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	12,027	6,300
Substandard Nonaccrual [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	$ 3,893	$ 5,659