DERIVATIVES - Derivatives Notional Amount (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Interest rate swaps
Derivative [Line Items]
Derivative asset, notional amount	$ 15,410,000	$ 11,490,000
Interest rate swaps | TBAs, short position
Derivative [Line Items]
Notional amount	$ 0	$ 0
Derivative, cap interest rate	0.00%	0.00%
Weighted average maturity	0 months	0 months
Interest rate swaps | TBAs, long position
Derivative [Line Items]
Notional amount	$ 15,400,000	$ 11,500,000
Derivative, cap interest rate	1.25%	1.10%
Weighted average maturity	42 months	42 months
Interest rate lock commitments
Derivative [Line Items]
Derivative asset, notional amount	$ 10,043,200	$ 10,653,850
TBAs | TBAs, short position
Derivative [Line Items]
Derivative liability, notional amount	29,386,167	22,697,706
Treasury futures
Derivative [Line Items]
Derivative liability, notional amount	0	314,500
Options on treasury futures
Derivative [Line Items]
Derivative asset, notional amount	$ 0	$ 3,200,000