LOAN PORTFOLIO - Corporation's TDR Activity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Schedule Of Financing Receivables [Line Items]
Beginning Balance of TDRs	$ 568,543	$ 670,991	$ 647,048		$ 661,591
New TDRs	29,101	15,596	83,368		66,075
Increases to existing TDRs (disbursements)	2,650	517	3,404		1,573
Charge-offs post modification	(2,949)	(5,445)	(26,976)	[1]	(15,899)
Sales	0	0	(53,245)		0
Foreclosures	(3,564)	(5,567)	(24,085)		(12,967)
Removed from TDR classification	0	0	0		(3,031)
Paid-off and partial payments	(7,986)	(19,774)	(43,719)		(41,024)
Ending balance of TDRs	$ 585,795	$ 656,318	$ 585,795		$ 656,318

[1] For the nine-month period ended September 30, 2017, includes a charge-off of $10.7 million related to the sale of the PREPA credit line.