INCOME TAXES - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Sep. 01, 2020
Income Tax Contingency [Line Items]
Maximum corporate tax rate	37.50%
Income tax expense	$ 31,935	$ 43,025
Minimum percentage of bank net taxable income for paying income tax at normal rate	20.00%
Estimated annual effective tax rate, including all entities	31.20%	32.90%
Santander [Member]
Income Tax Contingency [Line Items]
UTBs				$ 1,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 200
U S [Member]
Income Tax Contingency [Line Items]
Income tax expense	2,500	$ 1,600
Subsidiaries [Member]
Income Tax Contingency [Line Items]
Net deferred tax asset	154,800		$ 155,600
Valuation allowance	139,100		$ 149,500
Parent Company [Member]
Income Tax Contingency [Line Items]
Income tax expense	$ 1,078	$ 1,106
Domestic Country [Member] | Subsidiaries [Member]
Income Tax Contingency [Line Items]
Dividend received deduction	100.00%
Domestic Country [Member] | Other taxable domestic corporations [Member]
Income Tax Contingency [Line Items]
Dividend received deduction	85.00%