BORROWING ARRANGEMENTS (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Other borrowings		$ 23,172	$ 28,358
FHLB borrowings		832,527	972,744
Other borrowings:
Debt Instrument [Line Items]
Other borrowings		23,172	28,358
Average amount outstanding during the period	[1]	91,940	15,645
Maximum amount outstanding during the period	[2]	$ 219,259	$ 28,358
Weighted average interest rate during the period	[3]	0.40%	1.70%
Interest rate at end of period	[4]	0.10%	1.70%
FHLB borrowings:
Debt Instrument [Line Items]
FHLB borrowings		$ 832,527	$ 972,744
Average amount outstanding during the period	[1]	1,032,269	868,859
Maximum amount outstanding during the period	[2]	$ 1,274,370	$ 1,077,883
Weighted average interest rate during the period	[3]	1.10%	2.00%
Interest rate at end of period	[4]	1.00%	1.80%

[1] The average amount outstanding during the period was computed by dividing the total daily outstanding principal balances by the number of days in the period.

[2] The maximum amount outstanding at any month-end during the period.

[3] The weighted average interest rate during the period was computed by dividing the actual interest expense by the average amount outstanding during the period. The weighted average interest rate on the FHLB borrowings includes the effect of interest rate swaps.

[4] Stated rate.