SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE - Narratives (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Securities Sold Under Agreements To Repurchase And Other Short Term Borrowings [Line Items]
Assets Sold under Agreements to Repurchase, Interest Rate	2.46%		1.92%
Maximum aggregate balance outstanding	$ 150,086		$ 300,000
Weighted average interest rate	5.66%		3.64%
Repurchase Agreements [Member]
Securities Sold Under Agreements To Repurchase And Other Short Term Borrowings [Line Items]
Assets Sold under Agreements to Repurchase, Interest Rate		1.96%
Accrued interest payable on repurchase agreements	$ 2,800		$ 1,800
Maximum aggregate balance outstanding		$ 100,000
Maximum [Member]
Securities Sold Under Agreements To Repurchase And Other Short Term Borrowings [Line Items]
Maximum aggregate balance outstanding	200,000		300,000
Weighted Average [Member]
Securities Sold Under Agreements To Repurchase And Other Short Term Borrowings [Line Items]
Average balance outstanding	$ 166,000		$ 300,000