FEDERAL HOME LOAN BANK ADVANCES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
FEDERAL HOME LOAN BANK ADVANCES.
Average daily balance during the year	$ 324,653	$ 401,258
Average interest rate during the year (as a percent)	1.76%	1.52%
Maximum month-end balance during the year	$ 520,092	$ 563,974
Weighted average interest rate at year-end (as a percent)	2.72%	1.57%