INVESTMENTS (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Net unrealized gain on available-for-sale debt securities, net of tax	$ 11,801	$ 22,180	$ 29,310	$ 3,250
Deferred tax assets, unrealized losses on available for sale securities	3,200		8,000
Security pledged as collateral, amortized cost	484,300		485,000
Security pledged as collateral, fair value	495,400		507,100
Trading securities	4,123		4,161
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		0
Debt Securities, Available-for-sale, Realized Gain (Loss)	0	$ 0
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0		0
Debt Securities, Held-to-Maturity, Excluded Accrued Interest from Amortized Cost	8		10
Available-for-sale Securities
Schedule of Investments [Line Items]
Interest Receivable	$ 3,100		$ 3,100