Derivatives and Hedging Activities (Details Textual) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013 Contract	Jun. 30, 2012 Contract	Jun. 30, 2013 Contract	Jun. 30, 2012 Contract	Dec. 31, 2012 Contract
Credit risk
Derivatives and Hedging Activities (Textual) [Abstract]
Collateral pledged toward derivatives	$ 18,200,000		$ 18,200,000
Fair value hedging of interest rate risk
Derivatives and Hedging Activities (Textual) [Abstract]
Number of derivative contracts outstanding	25	7	25	7
Derivative instruments outstanding	8		8
Recognized net gain (loss) related to ineffectiveness of the fair value hedging relationships	289,000	(223,000)	203,000	(189,000)
Net reduction of interest expense	283,000		295,000
Remaining number of derivative held	17		17
Derivatives and Hedging Activities (Additional Textual) [Abstract]
Aggregate notional amount designated as fair value hedges of interest rate risk	335,000,000	104,000,000	335,000,000	104,000,000
Aggregate notional amount designated as fair value hedges of interest rate risk on outstanding swap	86,000,000		86,000,000
Cash flow hedging
Derivatives and Hedging Activities (Textual) [Abstract]
Number of derivative contracts outstanding	3	2	3	2	3
Recognized net gain (loss) related to ineffectiveness of the fair value hedging relationships			79,000
Deferred gains on terminated cash flow hedging	3,000	43,000	4,000	124,000
Estimated additional amount of deferred gains reclassified to interest revenue			58,000
Increase to deposit interest expense			862,000
Derivatives and Hedging Activities (Additional Textual) [Abstract]
Total notional amount designated as cash flow hedges	200,000,000		200,000,000
Aggregate notional amount designated as fair value hedges of interest rate risk on outstanding swap	375,000,000	200,000,000	375,000,000	200,000,000	200,000,000
Interest expense | Fair value hedging of interest rate risk
Derivatives and Hedging Activities (Textual) [Abstract]
Net reduction of interest expense	$ 1,200,000	$ 550,000	$ 2,270,000	$ 828,000