SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE AND OTHER SHORT-TERM DEBT - Contractual Maturity of Secured Borrowings and Class of Collateral Pledged (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Available-for-sale Securities Pledged as Collateral	$ 241,964	$ 185,963
Held-to-maturity Securities Pledged as Collateral	70,154	100,676
Overnight and Continuous
Available-for-sale Securities Pledged as Collateral	241,964	185,533
Held-to-maturity Securities Pledged as Collateral	70,154	100,676
Greater than 90 Days
Available-for-sale Securities Pledged as Collateral		430
U.S. Treasury Obligations
Available-for-sale Securities Pledged as Collateral	24,207	23,902
U.S. Treasury Obligations | Overnight and Continuous
Available-for-sale Securities Pledged as Collateral	24,207	23,902
U.S. Agency Obligations
Held-to-maturity Securities Pledged as Collateral	16,646	14,524
U.S. Agency Obligations | Overnight and Continuous
Held-to-maturity Securities Pledged as Collateral	16,646	14,524
U.S. GSEs
Available-for-sale Securities Pledged as Collateral	51,847	21,719
U.S. GSEs | Overnight and Continuous
Available-for-sale Securities Pledged as Collateral	51,847	21,719
FHLB Obligations
Available-for-sale Securities Pledged as Collateral	59,505	42,681
FHLB Obligations | Overnight and Continuous
Available-for-sale Securities Pledged as Collateral	59,505	42,681
Agency MBSs
Available-for-sale Securities Pledged as Collateral	44,736	49,592
Held-to-maturity Securities Pledged as Collateral		19,263
Agency MBSs | Overnight and Continuous
Available-for-sale Securities Pledged as Collateral	44,736	49,162
Held-to-maturity Securities Pledged as Collateral		19,263
Agency MBSs | Greater than 90 Days
Available-for-sale Securities Pledged as Collateral		430
Agency CMBSs
Available-for-sale Securities Pledged as Collateral	21,662	14,957
Held-to-maturity Securities Pledged as Collateral	53,508
Agency CMBSs | Overnight and Continuous
Available-for-sale Securities Pledged as Collateral	21,662	14,957
Held-to-maturity Securities Pledged as Collateral	53,508
Agency CMOs
Available-for-sale Securities Pledged as Collateral	40,007	33,112
Held-to-maturity Securities Pledged as Collateral		66,889
Agency CMOs | Overnight and Continuous
Available-for-sale Securities Pledged as Collateral	$ 40,007	33,112
Held-to-maturity Securities Pledged as Collateral		$ 66,889