DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Notional Amounts and Gross Fair Values (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Derivatives, Fair Value [Line Items]
Notional amount	$ 13,530.0	$ 14,526.0
Derivative asset, not offset against collateral	40.0	3.0
Derivative liability, not offset against collateral	9.0	20.0
Derivative asset, not subject to master netting arrangement	17.0	182.0
Derivative liability, not subject to master netting arrangement	257.0	25.0
Fair value, asset	57.0	185.0
Fair value, liability	266.0	45.0
Interest rate contracts – designated
Derivatives, Fair Value [Line Items]
Derivative asset, not offset against collateral	0.0	1.0
Derivative liability, not offset against collateral	0.0	0.0
Interest rate swaps – not designated
Derivatives, Fair Value [Line Items]
Derivative asset, not offset against collateral	40.0	2.0
Derivative liability, not offset against collateral	9.0	20.0
Derivative asset, not subject to master netting arrangement	14.0	172.0
Derivative liability, not subject to master netting arrangement	242.0	24.0
Interest rate lock commitments – not designated
Derivatives, Fair Value [Line Items]
Derivative asset, not subject to master netting arrangement	1.0	9.0
Derivative liability, not subject to master netting arrangement	15.0	0.0
Forward delivery commitments – not designated
Derivatives, Fair Value [Line Items]
Derivative asset, not subject to master netting arrangement	2.0	1.0
Derivative liability, not subject to master netting arrangement	0.0	1.0
Credit risk contracts – not designated
Derivatives, Fair Value [Line Items]
Notional amount	286.3
Derivative asset, not subject to master netting arrangement	0.0	0.0
Derivative liability, not subject to master netting arrangement	0.0	0.0
Subject to master netting arrangements:
Derivatives, Fair Value [Line Items]
Notional amount	7,290.0	7,627.0
Subject to master netting arrangements: \| Interest rate contracts – designated
Derivatives, Fair Value [Line Items]
Notional amount	1,980.0	2,080.0
Subject to master netting arrangements: \| Interest rate swaps – not designated
Derivatives, Fair Value [Line Items]
Notional amount	5,310.0	5,547.0
Not subject to master netting arrangements:
Derivatives, Fair Value [Line Items]
Notional amount	6,240.0	6,899.0
Not subject to master netting arrangements: \| Interest rate swaps – not designated
Derivatives, Fair Value [Line Items]
Notional amount	5,310.0	5,547.0
Not subject to master netting arrangements: \| Interest rate lock commitments – not designated
Derivatives, Fair Value [Line Items]
Notional amount	265.0	482.0
Not subject to master netting arrangements: \| Forward delivery commitments – not designated
Derivatives, Fair Value [Line Items]
Notional amount	280.0	502.0
Not subject to master netting arrangements: \| Credit risk contracts – not designated
Derivatives, Fair Value [Line Items]
Notional amount	$ 385.0	$ 368.0

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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