FINANCIAL DERIVATIVES - Schedule of Derivative Instruments in Statement of Financial Position (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Notional Disclosures [Abstract]
Notional Amount	$ 24,605,848	$ 24,896,331
Asset
Fair value, asset	32,667	27,789
Netting adjustments	(3,595)	(462)
(Liability)
Fair value, liability	(29,161)	(77,326)
Netting adjustments	3,595	462
Designated as hedge | Fair value hedges: | Receive fixed non-callable
Notional Disclosures [Abstract]
Notional Amount	6,913,685	9,657,181
Asset
Fair value, asset	2,084	5,134
(Liability)
Fair value, liability	$ (3,320)	$ (97)
Weighted- Average Pay Rate	4.45%	2.67%
Weighted- Average Receive Rate	3.52%	4.56%
Weighted- Average Remaining Term (in years)	1 year 2 months 15 days	9 years 1 month 13 days
Designated as hedge | Fair value hedges: | Pay fixed non-callable
Notional Disclosures [Abstract]
Notional Amount	$ 10,324,870	$ 7,460,685
Asset
Fair value, asset	2,067	174
(Liability)
Fair value, liability	$ (3,379)	$ (12,165)
Weighted- Average Pay Rate	2.79%	4.71%
Weighted- Average Receive Rate	4.30%	3.40%
Weighted- Average Remaining Term (in years)	8 years 9 months	1 year 6 months 10 days
Designated as hedge | Fair value hedges: | Receive fixed callable
Notional Disclosures [Abstract]
Notional Amount	$ 4,747,883	$ 4,592,077
Asset
Fair value, asset	21,310	5,119
(Liability)
Fair value, liability	$ (25,572)	$ (65,167)
Weighted- Average Pay Rate	4.32%	4.54%
Weighted- Average Receive Rate	3.76%	3.67%
Weighted- Average Remaining Term (in years)	3 years 14 days	2 years 7 months 24 days
Designated as hedge | Cash flow hedges: | Pay fixed non-callable
Notional Disclosures [Abstract]
Notional Amount	$ 463,000	$ 540,000
Asset
Fair value, asset	9,965	16,903
(Liability)
Fair value, liability	$ (123)	$ (2)
Weighted- Average Pay Rate	1.93%	1.92%
Weighted- Average Receive Rate	4.63%	4.87%
Weighted- Average Remaining Term (in years)	3 years 2 months 4 days	3 years 5 months 4 days
No hedge designation | Receive fixed non-callable
Notional Disclosures [Abstract]
Notional Amount	$ 1,390,415	$ 1,803,328
Asset
Fair value, asset	189	48
(Liability)
Fair value, liability	$ 0	$ (2)
Weighted- Average Pay Rate	4.28%	4.52%
Weighted- Average Receive Rate	4.00%	4.43%
Weighted- Average Remaining Term (in years)	5 months 1 day	3 months 18 days
No hedge designation | Pay fixed non-callable
Notional Disclosures [Abstract]
Notional Amount	$ 151,559	$ 157,776
Asset
Fair value, asset	443	819
(Liability)
Fair value, liability	$ (77)	$ (1)
Weighted- Average Pay Rate	2.97%	2.92%
Weighted- Average Receive Rate	4.50%	4.75%
Weighted- Average Remaining Term (in years)	3 years 3 days	3 years 4 months 24 days
No hedge designation | Basis swaps
Notional Disclosures [Abstract]
Notional Amount	$ 614,384	$ 655,384
Asset
Fair value, asset	2	8
(Liability)
Fair value, liability	$ (274)	$ (354)
Weighted- Average Pay Rate	4.43%	4.69%
Weighted- Average Receive Rate	4.27%	4.52%
Weighted- Average Remaining Term (in years)	3 years 3 months 21 days	3 years 9 months 29 days
No hedge designation | Treasury futures
Notional Disclosures [Abstract]
Notional Amount	$ 52	$ 29,900
Asset
Fair value, asset	202	46
Netting adjustments	(3,595)	(462)
(Liability)
Fair value, liability	(11)	0
Netting adjustments	$ 3,595	$ 462
Weighted- Average Forward Price (in dollars per share)	$ 112.87	$ 108.91