INVESTMENT SECURITIES - Narrative (Details)	9 Months Ended
	Sep. 30, 2021 position
Investments, Debt and Equity Securities [Abstract]
Maximum individual state general bond obligation as a percentage of total debt securities (percent)	1.00%
Securities in unrealized loss positions, number of positions	540
Securities, number of positions	1,740
S&P AA- rating
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of debt securities considered to be of investment-grade (percent)	96.00%