LOAN PORTFOLIO - Activity for Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Impaired Loans:
Balance at beginning of period	$ 735,625	$ 953,774	$ 887,905		$ 806,509
Loans determined impaired during the period	71,884	26,613	110,488		261,544
Charge-offs	(6,472)	(30,426)	(66,959)	[1]	(50,027)
Loans sold, net charge-offs	0	0	(53,245)		0
Increases to impaired loans (disbursements)	3,215	1,091	4,454		2,852
Foreclosures	(5,657)	(11,856)	(36,347)		(28,466)
Loans no longer considered impaired	(542)	(2,674)	(3,324)		(27,560)
Paid in full or partial payments	(18,794)	(23,668)	(63,713)		(51,998)
Transfer Of Impaired Loans Held For Sale To Portfolio Loans			0
Balance at end of period	$ 779,259	$ 912,854	$ 779,259		$ 912,854

[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, as further discussed below.