Loans Receivable and Allowance for Loan Losses (Summary of Loans Receivable) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Qualifying loans pledged as FHLB collateral	$ 465,300,000
Bank loans receivable, Gross	2,003,710,000	1,998,534,000
Bank loans receivable, Allowance for loan losses	25,755,000	24,998,000	23,934,000	23,110,000
Bank loans receivable, Net	1,977,955,000	1,973,536,000
Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	536,349,000	525,127,000
Bank loans receivable, Allowance for loan losses	12,019,000	11,714,000	7,914,000	8,178,000
Commercial tax-exempt [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	67,176,000	71,151,000
Bank loans receivable, Allowance for loan losses	52,000	55,000	68,000	72,000
Owner occupied real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	311,259,000	332,070,000
Bank loans receivable, Allowance for loan losses	1,944,000	1,931,000	2,236,000	2,180,000
Commercial construction and land development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	137,063,000	138,064,000
Bank loans receivable, Allowance for loan losses	4,529,000	4,242,000	5,842,000	5,559,000
Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	607,400,000	594,276,000
Bank loans receivable, Allowance for loan losses	4,945,000	4,707,000	4,640,000	4,161,000
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	116,143,000	110,951,000
Bank loans receivable, Allowance for loan losses	803,000	796,000	1,023,000	960,000
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	228,320,000	226,895,000
Bank loans receivable, Allowance for loan losses	$ 870,000	$ 931,000	$ 1,329,000	$ 1,303,000

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Amount of the collateral pledged in support of federal home loan bank advances outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 45

-Paragraph 1

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-Paragraph 3

-Subparagraph (d)

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-SubTopic 210

-Section S99

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-Subparagraph (SX 210.9-03.7(d))

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-Section L

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

+ References

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