INVESTMENT SECURITIES - Aggregate amortized cost and market value of the securities by issuers (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Federal Home Loan Mortgage Corporation Certificates And Obligations F H L M C [Member]
Schedule Of Available-For-Sale And Held-To-Maturity Securities [Line Items]
Amortized Cost	$ 340,227	$ 332,848
Fair Value	340,723	322,268
Government National Mortgage Association Certificates And Obligations G N M A [Member]
Schedule Of Available-For-Sale And Held-To-Maturity Securities [Line Items]
Amortized Cost	355,989	426,475
Fair Value	377,448	445,008
Federal National Mortgage Association Certificates And Obligations F N M A [Member]
Schedule Of Available-For-Sale And Held-To-Maturity Securities [Line Items]
Amortized Cost	922,883	891,952
Fair Value	926,189	861,783
FHLB [Member]
Schedule Of Available-For-Sale And Held-To-Maturity Securities [Line Items]
Amortized Cost	232,733	264,271
Fair Value	$ 227,003	$ 249,495