INVESTMENT SECURITIES (Details 6) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014
Scheduled maturities of investment securities available-for sale, amortized cost basis
Due within one year	$ 395,151
Due after one year through five years	505,195
Due after five years through ten years	608,053
Due after ten years	996,356
Total investment securities available-for-sale	2,504,755
Scheduled maturities of investment securities available-for sale, estimated fair value
Due within one year	384,287
Due after one year through five years	501,542
Due after five years through ten years	602,553
Due after ten years	986,362
Total investment securities available-for-sale	$ 2,474,744