DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Schedule of Notional Amounts and Gross Fair Values (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Derivatives, Fair Value [Line Items]
Notional amount	$ 15,744.0	$ 15,924.0
Derivative asset, not offset against collateral	74.0	96.0
Derivative liability, not offset against collateral	37.0	22.0
Derivative asset, not subject to master netting arrangement	41.0	21.0
Not subject to master netting arrangement	220.0	291.0
Fair value, asset	115.0	117.0
Fair value, liability	257.0	313.0
Interest rate contracts – designated
Derivatives, Fair Value [Line Items]
Derivative asset, not offset against collateral	6.0	0.0
Derivative liability, not offset against collateral	0.0	6.0
Interest rate swaps – not designated
Derivatives, Fair Value [Line Items]
Derivative asset, not offset against collateral	68.0	96.0
Derivative liability, not offset against collateral	37.0	16.0
Derivative asset, not subject to master netting arrangement	37.0	16.0
Not subject to master netting arrangement	218.0	287.0
Interest rate lock commitments – not designated
Derivatives, Fair Value [Line Items]
Derivative asset, not subject to master netting arrangement	4.0	1.0
Not subject to master netting arrangement	1.0	4.0
Forward delivery commitments – not designated
Derivatives, Fair Value [Line Items]
Derivative asset, not subject to master netting arrangement	0.0	4.0
Not subject to master netting arrangement	1.0	0.0
Credit risk contracts – not designated
Derivatives, Fair Value [Line Items]
Notional amount	577.0
Derivative asset, not subject to master netting arrangement	0.0	0.0
Not subject to master netting arrangement	0.0	0.0
Subject to master netting arrangements:
Derivatives, Fair Value [Line Items]
Notional amount	8,138.0	8,301.0
Subject to master netting arrangements: | Interest rate contracts – designated
Derivatives, Fair Value [Line Items]
Notional amount	2,150.0	2,400.0
Subject to master netting arrangements: | Interest rate swaps – not designated
Derivatives, Fair Value [Line Items]
Notional amount	5,988.0	5,901.0
Not subject to master netting arrangements:
Derivatives, Fair Value [Line Items]
Notional amount	7,606.0	7,623.0
Not subject to master netting arrangements: | Interest rate swaps – not designated
Derivatives, Fair Value [Line Items]
Notional amount	5,988.0	5,901.0
Not subject to master netting arrangements: | Interest rate lock commitments – not designated
Derivatives, Fair Value [Line Items]
Notional amount	413.0	417.0
Not subject to master netting arrangements: | Forward delivery commitments – not designated
Derivatives, Fair Value [Line Items]
Notional amount	449.0	486.0
Not subject to master netting arrangements: | Credit risk contracts – not designated
Derivatives, Fair Value [Line Items]
Notional amount	$ 756.0	$ 819.0