Loans - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income recognized			$ 3,000,000	$ 3,000,000
Transfers Of Financial Assets Accounted For As Sale Initial Fair Value Of Assets Obtained As Proceeds	$ 11,900,000	$ 36,684,000	36,903,000	300,051,000
Loans held in portfolio, net of unearned income	34,029,313,000		34,029,313,000		$ 32,077,769,000
Non-accrual with no allowance	144,321,000		144,321,000		177,104,000
Accumulated loans modified to borrowers under financial difficulties					1,644,647,000
Trading account debt securities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Transfers Of Financial Assets Accounted For As Sale Initial Fair Value Of Assets Obtained As Proceeds	11,599,000	35,875,000	35,958,000	294,872,000
Accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accumulated loans modified to borrowers under financial difficulties					1,495,309,000
Collateral Pledged
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	360,052,000		360,052,000		406,836,000
Non-accrual with no allowance	144,000,000		144,000,000		177,000,000
Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	1,207,488,000		1,207,488,000		1,294,617,000
Past due 90 days or more
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans past-due 90 days or more	264,212,000		264,212,000		351,614,000
Loans held in portfolio, net of unearned income	625,735,000		625,735,000		791,055,000
Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	32,821,825,000		32,821,825,000		30,783,152,000
GNMA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Repurchased loans			34,000,000	49,000,000
GNMA | Trading account debt securities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Transfers Of Financial Assets Accounted For As Sale Initial Fair Value Of Assets Obtained As Proceeds	1,421,000	14,190,000	2,488,000	169,352,000
FNMA | Trading account debt securities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Transfers Of Financial Assets Accounted For As Sale Initial Fair Value Of Assets Obtained As Proceeds	10,178,000	21,685,000	33,470,000	117,015,000
FHLMC | Trading account debt securities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Transfers Of Financial Assets Accounted For As Sale Initial Fair Value Of Assets Obtained As Proceeds	0		0	8,505,000
Consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of Loans	55,000,000	135,000,000	127,000,000	349,000,000
Loans Sold	45,000,000		45,000,000
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of Loans	102,000,000	66,000,000	274,000,000	219,000,000
Mortgage Loans Sold	12,000,000	17,000,000	39,000,000	50,000,000
Commercial Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of Loans	79,000,000	106,000,000	162,000,000	129,000,000
Loans Sold	45,000,000	11,000,000	81,000,000	54,000,000
Purchased credit deterioration loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchase of Loans	200,000	$ 300,000	900,000	$ 4,000,000
Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	7,585,111,000		7,585,111,000		7,397,471,000
Non-accrual with no allowance	91,119,000		91,119,000		119,098,000
Accumulated loans modified to borrowers under financial difficulties					1,256,766,000
Mortgages | Accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accumulated loans modified to borrowers under financial difficulties					1,169,976,000
Mortgages | Collateral Pledged
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	101,200,000		101,200,000		129,173,000
Mortgages | Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	808,310,000		808,310,000		937,253,000
Mortgages | Past due 90 days or more
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans past-due 90 days or more	242,987,000		242,987,000		337,602,000
Loans held in portfolio, net of unearned income	442,410,000		442,410,000		600,481,000
Mortgages | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	6,776,801,000		6,776,801,000		6,460,218,000
Mortgages | US Government Agency Insured Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	2,100,000,000		2,100,000,000		2,000,000,000.0
Mortgages | US Government Agency Insured Loans | Past due 90 days or more
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	200,000,000		200,000,000		300,000,000
Mortgages | Guaranteed by U.S. sponsored entities | Accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accumulated loans modified to borrowers under financial difficulties					725,000,000
Mortgages | GNMA | Buy Back Option Program | Past due 90 days or more
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans past-due 90 days or more	8,000,000		8,000,000		14,000,000
Reverse Mortgages | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	39,000,000		39,000,000		42,000,000
Residential mortgage loans insured By FHA
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual with no allowance	115,000,000		115,000,000		190,000,000
Puerto Rico
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	23,762,570,000		23,762,570,000		22,546,905,000
Non-accrual with no allowance	139,936,000		139,936,000		170,484,000
Puerto Rico | Collateral Pledged
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	348,233,000		348,233,000		399,047,000
Puerto Rico | Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	1,141,154,000		1,141,154,000		1,213,179,000
Puerto Rico | Past due 90 days or more
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans past-due 90 days or more	264,082,000		264,082,000		351,248,000
Loans held in portfolio, net of unearned income	597,907,000		597,907,000		753,257,000
Puerto Rico | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	22,621,416,000		22,621,416,000		21,333,726,000
Puerto Rico | Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	6,289,268,000		6,289,268,000		6,110,279,000
Non-accrual with no allowance	90,611,000		90,611,000		119,027,000
Puerto Rico | Mortgages | Collateral Pledged
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	100,127,000		100,127,000		128,069,000
Puerto Rico | Mortgages | Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	773,071,000		773,071,000		894,800,000
Puerto Rico | Mortgages | Past due 90 days or more
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accruing loans past-due 90 days or more	242,987,000		242,987,000		337,602,000
Loans held in portfolio, net of unearned income	430,430,000		430,430,000		579,993,000
Puerto Rico | Mortgages | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	5,516,197,000		5,516,197,000		5,215,479,000
Puerto Rico | Reverse Mortgages | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held in portfolio, net of unearned income	39,000,000		39,000,000		42,000,000
Puerto Rico | Residential mortgage loans insured By FHA | Past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual with no allowance	$ 115,000,000		$ 115,000,000		$ 190,000,000