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Securities Available for Sale - Schedule of Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of AFS Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Mar. 31, 2026	Dec. 31, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 4,103,026		$ 3,733,780
Gross Unrealized Gains	9,228		27,237
Gross Unrealized Losses	(61,512)		(50,215)
Allowance for Credit Losses	(3,981)		(4,093)
Fair Value	4,046,761		3,706,709
Senior asset-backed securities related to Structured Program transactions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,390,657		3,065,885
Gross Unrealized Gains	8,791		26,525
Gross Unrealized Losses	(5,394)		0
Allowance for Credit Losses	0		0
Fair Value	3,394,054		3,092,410
Other asset-backed securities related to Structured Program transactions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	266,096		224,802
Gross Unrealized Gains	186		28
Gross Unrealized Losses	(4,481)		(1,367)
Allowance for Credit Losses	(3,981)	$ (3,816)	(4,093)	$ (4,029)	$ (4,848)	$ (3,527)
Fair Value	257,820		219,370
Restricted investments	226,700		200,000
U.S. agency residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	277,218		267,853
Gross Unrealized Gains	235		504
Gross Unrealized Losses	(34,078)		(32,296)
Allowance for Credit Losses	0		0
Fair Value	243,375		236,061
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	81,467		84,464
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(11,185)		(10,602)
Allowance for Credit Losses	0		0
Fair Value	70,282		73,862
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	59,188		60,423
Gross Unrealized Gains	16		135
Gross Unrealized Losses	(5,398)		(4,961)
Allowance for Credit Losses	0		0
Fair Value	53,806		55,597
Municipal securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,205		3,215
Gross Unrealized Gains	0		0
Gross Unrealized Losses	(527)		(609)
Allowance for Credit Losses	0		0
Fair Value	2,678		2,606
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	25,195		27,138
Gross Unrealized Gains	0		45
Gross Unrealized Losses	(449)		(380)
Allowance for Credit Losses	0		0
Fair Value	$ 24,746		$ 26,803