Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Available-for-sale, Amortized Cost
Due after one through five years	$ 924
Due after five through ten years	52,757
Due after ten years	20,789
Agency mortgage-backed securities	262,710
Total	337,180
Available-for-sale, Estimated Fair Value
Due after one through five years	963
Due after five through ten years	53,929
Due after ten years	20,831
Agency mortgage-backed securities	271,077
Estimated Fair Value	346,800	367,912
Held-to-maturity, Amortized Cost
Due after five through ten years	1,085
Due after ten years	52,013
Agency mortgage-backed securities	15,185
Total	68,283
Held-to-maturity, Estimated Fair Value
Due after five through ten years	1,060
Due after ten years	49,706
Agency mortgage-backed securities	14,893
Total	$ 65,659