Note FDIC loss share asset (FDIC loss share - Additional Information) (Detail) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2018 USD ($) D		Mar. 31, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) D		Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition, Contingent Consideration [Line Items]
True Up Payment Term | D	45				45
OREO transfer to non-covered status	$ 0	[1]	$ 15,300		$ 0	[2]
Loans transfer to non-covered status			514,600
Payment to the FDIC as a consideration for the termination of the loss share agreement.	23,700
True-up payment obligation			171,000					$ 165,000
FDIC loss-share asset net	0		45,600	$ 52,583	0		$ 52,583
Balance Due To F D I C	0		$ 1,100	(487)	0		(487)
Gain on FDIC LSA termination agreement	102,752	[3]		$ 0	102,752	[3]	$ 0
Non-covered loans | Mortgages
Business Acquisition, Contingent Consideration [Line Items]
OREO transfer to non-covered status	$ 15,333	[1]			$ 15,333	[2]
Banco Popular de Puerto Rico
Business Acquisition, Contingent Consideration [Line Items]
Loss Sharing Agreement Allocation Percentage					80.00%

[1] Represents the reclassification of OREOs to the non-covered category, pursuant to the Termination Agreement of all shared-loss agreements with the Federal Deposit Insurance Corporation related to loans acquired from Westernbank, that was completed on May 22, 2018.

[2] Represents the reclassification of OREOs to the non-covered category, pursuant to the Termination Agreement of all shared-loss agreements with the Federal Deposit Insurance Corporation related to loans acquired from Westernbank, that was completed on May 22, 2018.

[3] Refer to Note 9 for additional information of the Termination Agreement with the FDIC.