INVESTMENT SECURITIES - Schedule of Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Investment securities
Available-for-sale:
Amount Outstanding	$ 6,183,545	$ 5,120,963
Amortized cost	6,105,116	5,060,135
Allowance for losses	(27)	(27)
Unrealized Gains	9,514	9,844
Unrealized Losses	(161,589)	(151,021)
Fair Value	5,953,014	4,918,931
Held-to-maturity:
Amount Outstanding	9,270	53,756
Amortized cost	9,270	53,756
Allowance for losses	0	0
Unrealized Gains	270	1,745
Unrealized Losses	0	0
Fair Value	9,540	55,501
Available-for-sale, accrued interest excluded	22,300	15,900
Available-for-Sale Securities \| Investment securities
Available-for-sale:
Unamortized Premium/(Discount)	(78,429)	(60,828)
Held-to-maturity:
Unamortized Premium/(Discount)	(78,429)	(60,828)
Held-to-Maturity Securities \| Investment securities
Available-for-sale:
Unamortized Premium/(Discount)	0	0
Held-to-maturity:
Unamortized Premium/(Discount)	0	0
Floating interest rate \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Available-for-sale:
Amount Outstanding	19,700	19,700
Amortized cost	19,700	19,700
Allowance for losses	(27)	(27)
Unrealized Gains	0	0
Unrealized Losses	(197)	(591)
Fair Value	19,476	19,082
Floating interest rate \| Guaranteed mortgage-backed securities
Available-for-sale:
Amount Outstanding	2,317,032	2,454,009
Amortized cost	2,316,191	2,452,871
Allowance for losses	0	0
Unrealized Gains	3,484	1,212
Unrealized Losses	(13,950)	(29,649)
Fair Value	2,305,725	2,424,434
Floating interest rate \| US Treasuries
Available-for-sale:
Amount Outstanding	0	50,000
Amortized cost	0	49,983
Allowance for losses	0	0
Unrealized Gains	0	0
Unrealized Losses	0	(15)
Fair Value	0	49,968
Floating interest rate \| Available-for-Sale Securities \| Floating rate auction-rate certificates backed by Government guaranteed student loans
Available-for-sale:
Unamortized Premium/(Discount)	0	0
Held-to-maturity:
Unamortized Premium/(Discount)	0	0
Floating interest rate \| Available-for-Sale Securities \| Guaranteed mortgage-backed securities
Available-for-sale:
Unamortized Premium/(Discount)	(841)	(1,138)
Held-to-maturity:
Unamortized Premium/(Discount)	(841)	(1,138)
Floating interest rate \| Available-for-Sale Securities \| US Treasuries
Available-for-sale:
Unamortized Premium/(Discount)	0	(17)
Held-to-maturity:
Unamortized Premium/(Discount)	0	(17)
Fixed Interest Rate \| Guaranteed mortgage-backed securities
Available-for-sale:
Amount Outstanding	2,544,136	1,727,669
Amortized cost	2,477,291	1,680,881
Allowance for losses	0	0
Unrealized Gains	3,426	6,558
Unrealized Losses	(142,750)	(117,824)
Fair Value	2,337,967	1,569,615
Held-to-maturity:
Amount Outstanding	9,270	53,756
Amortized cost	9,270	53,756
Allowance for losses	0	0
Unrealized Gains	270	1,745
Unrealized Losses	0	0
Fair Value	$ 9,540	$ 55,501
Held-to-maturity investment securities weighted average yield	6.40%	6.70%
Fixed Interest Rate \| US Treasuries
Available-for-sale:
Amount Outstanding	$ 1,302,677	$ 869,585
Amortized cost	1,291,934	856,700
Allowance for losses	0	0
Unrealized Gains	2,604	2,074
Unrealized Losses	(4,692)	(2,942)
Fair Value	1,289,846	855,832
Fixed Interest Rate \| Available-for-Sale Securities \| Guaranteed mortgage-backed securities
Available-for-sale:
Unamortized Premium/(Discount)	(66,845)	(46,788)
Held-to-maturity:
Unamortized Premium/(Discount)	(66,845)	(46,788)
Fixed Interest Rate \| Available-for-Sale Securities \| US Treasuries
Available-for-sale:
Unamortized Premium/(Discount)	(10,743)	(12,885)
Held-to-maturity:
Unamortized Premium/(Discount)	(10,743)	(12,885)
Fixed Interest Rate \| Held-to-Maturity Securities \| Guaranteed mortgage-backed securities
Available-for-sale:
Unamortized Premium/(Discount)	0	0
Held-to-maturity:
Unamortized Premium/(Discount)	$ 0	$ 0

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