Loans Receivable and Allowance for Loan Losses (Credit Quality Indicators for Commercial Loans, by Loan Type) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	$ 1,210,761	$ 1,150,450
Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	347,099	321,988
Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	88,934	81,532
Owner occupied real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	274,235	279,372
Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	107,311	103,153
Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	393,182	364,405
Pass Rated Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	1,114,360	1,047,702
Pass Rated Loans [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	303,421	280,884
Pass Rated Loans [Member] | Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	88,934	77,657
Pass Rated Loans [Member] | Owner occupied real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	257,162	263,001
Pass Rated Loans [Member] | Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	87,130	76,374
Pass Rated Loans [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	377,713	349,786
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	18,304	19,803
Special Mention [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	6,936	9,176
Special Mention [Member] | Commercial tax-exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	0	3,875
Special Mention [Member] | Owner occupied real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	4,308	2,887
Special Mention [Member] | Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	5,338	3,071
Special Mention [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	1,722	794
Substandard Accrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	46,337	53,557
Substandard Accrual [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	19,609	21,766
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	9,535	10,589
Substandard Accrual [Member] | Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	8,017	15,197
Substandard Accrual [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	9,176	6,005
Substandard Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	31,760	29,388
Substandard Nonaccrual [Member] | Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	17,133	10,162
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	3,230	2,895
Substandard Nonaccrual [Member] | Commercial construction and land development [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	6,826	8,511
Substandard Nonaccrual [Member] | Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Credit exposure for commercial loans	$ 4,571	$ 7,820