Securities (Details 1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Maturities of debt securities available for sale
Due within one year, Amortized Cost	$ 420	$ 345
Due in one to five years, Amortized Cost	13,205	11,499
Due in five to ten years, Amortized Cost	31,888	30,007
Due in more than ten years, Amortized Cost	52,924	53,222
Total, Amortized Cost	98,437	95,073
Total unrestricted securities available for sale, Amortized Cost	339,502	340,488
Due within one year, Estimated Fair Value	420	346
Due in one to five years, Estimated Fair Value	13,378	11,682
Due in five to ten years, Estimated Fair Value	33,668	32,316
Due in more than ten years, Estimated Fair Value	56,106	57,290
Total, Estimated Fair Value	103,572	101,634
Total unrestricted securities available for sale, Estimated Fair Value	352,973	356,345
Amortizing agency bonds [Member]
Maturities of debt securities available for sale
Total, Amortized Cost	127,186	135,452
Total, Estimated Fair Value	132,079	140,416
Mortgage-backed securities [Member]
Maturities of debt securities available for sale
Total, Amortized Cost	113,879	109,963
Total, Estimated Fair Value	$ 117,322	$ 114,295