SECURITIES (Schedule of Amortized Cost and Estimated Fair Values of Debt Securities by Contractual Maturity) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Available-for-sale, Amortized Cost
Due in one year or less	$ 1,769
Due after one year through five years	23,249
Due after five years through ten years	133,781
Due after ten years	629,354
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Total	788,153
Available-for-sale, Fair Value
Due in one year or less	1,812
Due after one year through five years	24,102
Due after five years through ten years	138,478
Due after ten years	639,228
Available-for-sale Securities, Debt Securities, Total	$ 803,620