Securities (Details 2) (USD $)	Mar. 31, 2013 item	Dec. 31, 2012 item
Securities available for sale, Amortized Cost
Due in one year or less	$ 21,782,000	$ 17,100,000
Due after one year through five years	50,935,000	50,109,000
Due after five years through ten years	76,113,000	70,662,000
Due after ten years	122,566,000	111,158,000
Amortized Cost	271,396,000	249,029,000
Securities available for sale, Fair Value
Due in one year or less	22,386,000	17,604,000
Due after one year through five years	52,687,000	51,757,000
Due after five years through ten years	76,746,000	71,307,000
Due after ten years	122,784,000	111,299,000
Fair Value	274,603,000	251,967,000
Securities Held to Maturity, Amortized Cost
Due after one year through five years	7,309,000	7,395,000
Due after ten years	7,142,000	7,842,000
Amortized Cost	14,451,000	15,237,000
Securities held to maturity, Fair Value
Due after one year through five years	7,395,000	7,478,000
Due after ten years	7,394,000	8,128,000
Fair Value	14,789,000	15,606,000
Held to Maturity and Available-for-sale
Held to maturity and available-for-sale securities, Amortized Cost	285,847,000	264,266,000
Held to maturity and available-for-sale securities, Fair Value	289,392,000	267,573,000
Investment securities pledged as collateral	0	0
Unrealized loss positions
Unrealized losses attributable to securities that had been in an unrealized loss position for less than 12 months	288,000	332,000
Number of securities at unrealized loss position for less than 12 months	15	14
Unrealized losses attributable to securities that had been in an unrealized loss position for greater than 12 months	$ 270,000	$ 133,000
Number of securities at unrealized loss position for greater than 12 months	13	12