INCOME TAXES - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Income Tax Contingency [Line Items]
Maximum corporate tax rate			37.50%
Valuation allowance	$ 166,400		$ 166,400
Income tax expense	34,103	$ 40,092	$ 77,128	$ 68,114
Minimum percentage of bank net taxable income for paying income tax at normal rate			20.00%
Estimated annual effective tax rate, excluding entities from which a tax benefit cannot be recognized and discrete items			31.70%	33.20%
Estimated annual effective tax rate, including all entities			31.90%	33.60%
Effective Income Tax Rate Excluding Discrete Items			32.30%	33.80%
Deferred tax asset that will be realized	167,000		$ 167,000
Accrued interest and penalties related to uncertain tax positions	300		300
Santander [Member]
Income Tax Contingency [Line Items]
UTBs	1,000		1,000
U S [Member]
Income Tax Contingency [Line Items]
Current income tax expense	2,500	$ 1,400	4,100	$ 2,500
FirstBank [Member]
Income Tax Contingency [Line Items]
Valuation allowance	127,700		127,700		$ 69,700
Deferred tax asset that will be realized	$ 166,900		$ 166,900		$ 208,400
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%