Loans Receivable and Allowance for Loan Losses (Summary of Loans Receivable) (Details) (USD $)	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Qualifying loans pledged as FHLB collateral	$ 591,900,000
Bank loans receivable, Gross	1,913,620,000		1,750,872,000
Bank loans receivable, Allowance for loan losses	24,540,000	24,271,000	23,110,000	27,425,000	28,038,000	25,282,000
Bank loans receivable, Net	1,889,080,000		1,727,762,000
Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	478,605,000		447,144,000
Bank loans receivable, Allowance for loan losses	9,984,000	7,100,000	8,178,000	9,263,000	10,549,000	9,959,000
Commercial tax-exempt [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	75,986,000		81,734,000
Bank loans receivable, Allowance for loan losses	67,000	67,000	72,000	75,000	74,000	83,000
Owner occupied real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	312,032,000		302,417,000
Bank loans receivable, Allowance for loan losses	1,972,000	2,233,000	2,180,000	2,177,000	2,207,000	2,129,000
Commercial construction and land development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	122,314,000		133,176,000
Bank loans receivable, Allowance for loan losses	4,022,000	6,696,000	5,559,000	7,489,000	7,810,000	7,222,000
Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	594,004,000		473,188,000
Bank loans receivable, Allowance for loan losses	4,747,000	4,840,000	4,161,000	5,751,000	5,059,000	3,983,000
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	107,707,000		97,766,000
Bank loans receivable, Allowance for loan losses	1,604,000	1,061,000	960,000	879,000	863,000	324,000
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Bank loans receivable, Gross	222,972,000		215,447,000
Bank loans receivable, Allowance for loan losses	$ 1,366,000	$ 1,333,000	$ 1,303,000	$ 1,316,000	$ 1,258,000	$ 793,000