REPURCHASE AGREEMENTS (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets Sold under Agreements to Repurchase [Line Items]
Certificates of Deposit, at Carrying Value	$ 920	$ 920,000
Repurchase Agreements	256,274	244,646
Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	256,274	244,646
Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
30 - 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Greater than 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	256,274	244,646
Retail Customers | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	256,274	244,646
Retail Customers | Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers | 30 - 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers | Greater than 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers | Obligations of states and political subdivisions
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	1,125	630
Retail Customers | Obligations of states and political subdivisions | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	1,125	630
Retail Customers | Obligations of states and political subdivisions | Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers | Obligations of states and political subdivisions | 30 - 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers | Obligations of states and political subdivisions | Greater than 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers | Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	90,903	98,460
Retail Customers | Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	90,903	98,460
Retail Customers | Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises | Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers | Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises | 30 - 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers | Mortgage-backed securities issued or guaranteed by U.S. government-sponsored enterprises | Greater than 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers | Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	164,246	145,556
Retail Customers | Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises | Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	164,246	145,556
Retail Customers | Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises | Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers | Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises | 30 - 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	0	0
Retail Customers | Collateralized mortgage obligations issued or guaranteed by U.S. government-sponsored enterprises | Greater than 90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase Agreements	$ 0	$ 0