INVESTMENTS - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019
Gain (Loss) on Securities [Line Items]
Proceeds from Sale of Debt Securities, Available-for-sale	$ 1,300	$ 284,900	$ 42,600	$ 400,500
Available-for-sale Securities, Gross Realized Gains	26	1,200	100	1,900
Available-for-sale Securities, Gross Realized Losses	$ 24	1,100	$ 200	$ 1,800
Debt Securities, Held-to-maturity, Transfer, Amount		268,700
Realized gain (loss) on debt securities transferred from HTM to AFS		$ 200
NumberOfSecuritiesInSecurityPortfolio	1,291		1,291		1,273
NumberOfSecuritiesInUnrealizedLossPosition	119		119		140
Debt Securities, Held-to-maturity, Nonaccrual	$ 0		$ 0