Note Allowance for loan losses (Activity in Allowance for Loan Losses Related to ASC 310-30 Acquired Loans) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period	$ 544,496	$ 538,472	$ 540,651	$ 537,111
Provision for loan losses	52,479	40,472	93,177	85,307
Balance at end of period	540,014	548,720	540,014	548,720
Westernbank Puerto Rico | Acquired loans in an FDIC assisted transaction | Credit Impaired Loans | ASC Subtopic 310-30
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period	66,544	62,967	68,877	63,563
Provision for loan losses	5,541	(5,861)	5,219	(4,070)
Net recoveries (charge-offs)	(6,411)	9,889	(8,422)	7,502
Balance at end of period	$ 65,674	$ 66,995	$ 65,674	$ 66,995