FEDERAL HOME LOAN BANK ADVANCES - Contractual Maturities and Weighted Average Interest Rates of FHLB Advances (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Contractual Maturity, Amount
Overnight	$ 47,000
2019	290,000	$ 240,433
Total FHLB advances	$ 337,000	$ 240,433
Weighted Average Rate
Overnight (as a percent)	2.10%
2019 (as a percent)	2.14%	2.72%
Weighted Average Rate for total FHLB advances (as a percent)	2.13%	2.72%