v3.25.2

DESCRIPTION OF BUSINESS, BASIS OF PRESENTATION AND ACCOUNTING POLICIES - Sale of Subsidiary and Joint Venture with FDIC (Details)	1 Months Ended
	May 31, 2024 USD ($)	Jun. 30, 2025 USD ($)	Jun. 24, 2025 property	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Noncontrolling Interest [Line Items]
Disposal group, deposit		$ 596,555,000		$ 0
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Allentown, Pennsylvania Branches
Noncontrolling Interest [Line Items]
Number of bank branches held for sale \| property			7
Disposal group, deposit		600,000,000
Disposal group, retail and business loans		$ 30,000,000
Services and Promotions Delaware Corp
Noncontrolling Interest [Line Items]
Investments in subsidiaries, fair value	$ 134,000,000
Gain on sale of subsidiary	51,300,000
Sale of subsidiary, tax	$ 7,900,000
FDIC \| Structured LLC
Noncontrolling Interest [Line Items]
Equity ownership, excluding consolidated entity and equity method investee, percentage		20.00%		20.00%	20.00%
Joint venture, acquired amount		$ 1,100,000,000		$ 1,200,000,000	$ 1,100,000,000
Joint venture portfolio amount					$ 9,000,000,000

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Percentage of ownership of equity interest excluding interest in entity that is consolidated and equity method investee.

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Santander Holdings USA, Inc. 10-Q