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
	Mar. 31, 2017	Mar. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period	$ 540,651	$ 537,111
Provision for loan losses	40,698	44,835
Balance at end of period	544,496	538,472
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	68,877	63,563
Provision for loan losses	(322)	1,791
Net recoveries (charge-offs)	(2,011)	(2,387)
Balance at end of period	$ 66,544	$ 62,967