NATURAL DISASTERS- Additional information (Detail) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended	12 Months Ended
		Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2017
Liability For Catastrophe Claims [Line Items]
Financing Receivable Allowance For Credit Losses		$ 231,843	$ 231,843	$ 231,843	$ 205,603	$ 240,710
Loans And Leases Receivable Impaired Nonperforming Nonaccrual Of Interest	[1],[2],[3]	489,554	489,554	489,554	560,094
Marketing And Advertising Expense				12,485	11,419	15,234
Provision For Loan And Lease Losses				144,254	86,733	$ 172,045
Increase Decrease In Deposits Excluding Brokered Certificates Of Deposits		361,500
Increase Decrease In Non Interest Bearing Demand Deposits		$ 247,500
Percentage Of Non Interest Bearing Demand Deposits		16.00%
Hurricane [Member]
Liability For Catastrophe Claims [Line Items]
Financing Receivable Allowance For Credit Losses		$ 68,500	68,500	68,500			$ 66,500
Loss Contingency Receivable		4,800	4,800	4,800
Loss And Expenses Catastrophic Events				7,200
Disaster Response Plan Costs				6,600
Other Real Estate Owned Storm Related Expenses Not Recoverable				2,500
Provision For Loan And Lease Losses		4,800		$ 71,300
Hurricane Category Five Description				Category 5 hurricane
Hurricane Category Four Description				Category 4 hurricane
Residential Mortgage [Member]
Liability For Catastrophe Claims [Line Items]
Loans And Leases Receivable Impaired Nonperforming Nonaccrual Of Interest Additions			23,000
Loans And Leases Receivable Impaired Nonperforming Nonaccrual Of Interest		178,291	178,291	$ 178,291	160,867
Consumer Loan [Member]
Liability For Catastrophe Claims [Line Items]
Loans And Leases Receivable Impaired Nonperforming Nonaccrual Of Interest		5,370	5,370	5,370	$ 8,399
Commercial Portfolio Segment [Member]
Liability For Catastrophe Claims [Line Items]
Loans And Leases Receivable Impaired Nonperforming Nonaccrual Of Interest Additions			59,400
Loans And Leases Receivable Impaired Nonperforming Nonaccrual Of Interest		$ 294,400	$ 294,400	$ 294,400

[1] Amount excludes PCI loans with a carrying value of approximately $158.2 million and $165.8 million as of December 31, 2017 and 2016, respectively, primarily mortgage loans acquired from Doral Bank in the first quarter of 2015 and from Doral Financial in the second quarter of 2014, as further discussed below. These loans are not considered non-performing due to the application of the accretion method, under which these loans will accrete interest income over the remaining life of the loans using an estimated cash flow analysis.

[2] Excludes $8.3 million and $8.1 million of non-performing loans held for sale as of December 31, 2017 and 2016, respectively.

[3] Non-performing loans exclude $374.7 million and $384.9 million of TDR loans that are in compliance with the modified terms and in accrual status as of December 31, 2017 and 2016, respectively.