DERIVATIVE INSTRUMENTS - Summary of Characteristics of Interest Rate Swaps (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Interest rate swaps, at fair value
Derivative [Line Items]
Current Underlying Notional	$ 46,480,250,000	$ 45,907,300,000
Weighted Average Pay Rate	0.70%	0.59%
Weighted Average Receive Rate	0.50%	0.08%
Weighted Average Years to Maturity	3 years 7 months 28 days	3 years 3 months 25 days
Interest rate swaps, at fair value | LIBOR
Derivative [Line Items]
Notional Amount, Percentage	0.17	0.18
Interest rate swaps, at fair value | Federal funds index swap
Derivative [Line Items]
Notional Amount, Percentage	0.46	0.53
Interest rate swaps, at fair value | Secured Overnight Financing Rate
Derivative [Line Items]
Notional Amount, Percentage	0.37	0.29
Interest rate swaps, at fair value | 0 - 3 years
Derivative [Line Items]
Minimum Maturity Period	0 years	0 years
Maximum Maturity Period	3 years	3 years
Current Underlying Notional	$ 29,179,850,000	$ 32,709,300,000
Weighted Average Pay Rate	0.36%	0.25%
Weighted Average Receive Rate	0.53%	0.06%
Weighted Average Years to Maturity	9 months	1 year 1 month 6 days
Interest rate swaps, at fair value | 3 - 6 years
Derivative [Line Items]
Minimum Maturity Period	3 years	3 years
Maximum Maturity Period	6 years	6 years
Current Underlying Notional	$ 4,343,000,000	$ 2,780,000,000
Weighted Average Pay Rate	0.83%	0.21%
Weighted Average Receive Rate	0.32%	0.07%
Weighted Average Years to Maturity	3 years 9 months 29 days	3 years 5 months 15 days
Interest rate swaps, at fair value | 6 - 10 years
Derivative [Line Items]
Minimum Maturity Period	6 years	6 years
Maximum Maturity Period	10 years	10 years
Current Underlying Notional	$ 11,042,400,000	$ 9,118,000,000
Weighted Average Pay Rate	1.54%	1.43%
Weighted Average Receive Rate	0.47%	0.13%
Weighted Average Years to Maturity	9 years 3 days	9 years 18 days
Interest rate swaps, at fair value | Greater than 10 years
Derivative [Line Items]
Minimum Maturity Period	10 years	10 years
Current Underlying Notional	$ 1,915,000,000	$ 1,300,000,000
Weighted Average Pay Rate	3.45%	4.04%
Weighted Average Receive Rate	0.34%	0.11%
Weighted Average Years to Maturity	16 years 10 months 24 days	18 years 8 months 12 days
Forward starting pay fixed swaps
Derivative [Line Items]
Current Underlying Notional	$ 0	$ 0