DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Derivative [Line Items]
Notional amount	$ 13,733,000,000		$ 12,480,000,000
Additional amount in excess of posted collateral required in case of breached agreements	500,000		300,000
Subject to Master Netting Arrangement [Member]
Derivative [Line Items]
Notional amount	$ 6,912,000,000		6,221,000,000
Interest rate contracts [Member]
Derivative [Line Items]
Maximum length of time hedged in interest rate cash flow hedge	4 years
Period to reclassification of cash flow hedge gain loss	12 months
Derivative gains to be reclassified within twelve months	$ 14,500,000
Derivative gains to be reclassified within twelve months, net of tax	11,300,000
Derivative gain or losses excluded from assessment of hedge effectiveness	0
Amount of gain (loss) reclassified from AOCI into net income	0	$ 0
Interest rate contracts [Member] | Subject to Master Netting Arrangement [Member]
Derivative [Line Items]
Termination of derivative contract, notional amount		$ 225,000,000
Notional amount	1,580,000,000		1,430,000,000
Credit risk contracts - not designated [Member]
Derivative [Line Items]
Notional amount	261,800,000
Maximum exposure under credit risk agreement assuming customer default	300,000		600,000
Credit risk derivatives, purchased at fair value	100,000		200,000
Credit risk derivatives, sold at fair value	$ 300,000		$ 600,000
Credit risk contracts - not designated [Member] | Minimum [Member]
Derivative [Line Items]
Risk participation agreements, term	9 months
Credit risk contracts - not designated [Member] | Maximum [Member]
Derivative [Line Items]
Risk participation agreements, term	20 years