FDIC loss share - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) D	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) D	Jun. 30, 2014 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Business Acquisition, Contingent Consideration [Line Items]
True Up Payment Term | D	45		45
Calculation Percent Asset Discount Per Bid	$ 1,100,000,000		$ 1,100,000,000
Intrinsic Loss Estimate	4,600,000,000		$ 4,600,000,000
Servicing Amount Period Trueup Payment			twelve-month period
F D I C Indemnification Asset Accretion Of Discount	(31,065,000)	$ (72,095,000)	$ (58,381,000)	$ (121,041,000)
F D I C Indemnification Asset	392,947,000	$ 712,869,000	392,947,000	$ 712,869,000	$ 409,844,000	$ 542,454,000	$ 798,460,000	$ 909,414,000
Reclassification Of Loans Expiration LSA	1,500,000,000		1,500,000,000
Pending Dispute With FDIC [Member]
Business Acquisition, Contingent Consideration [Line Items]
Reclassification Of Loans Expiration LSA	248,700,000		$ 248,700,000
Payment Percentage True Up Payment [Member]
Business Acquisition, Contingent Consideration [Line Items]
Fixed Percentage True Up Payment			50.00%
Intrinsic Loss Estimate Trueup Payment [Member]
Business Acquisition, Contingent Consideration [Line Items]
Percent Calculation Intrinsic Loss Estimate	925,000,000		$ 925,000,000
Fixed Percentage True Up Payment			20.00%
Asset Discount Trueup Payment [Member]
Business Acquisition, Contingent Consideration [Line Items]
Fixed Percentage True Up Payment			25.00%
Cumulative Shared Loss Payments Trueup Payment [Member]
Business Acquisition, Contingent Consideration [Line Items]
Fixed Percentage True Up Payment			25.00%
Servicing Percentage Trueup Payment [Member]
Business Acquisition, Contingent Consideration [Line Items]
Fixed Percentage True Up Payment			1.00%
Banco Popular De Puerto Rico [Member]
Business Acquisition, Contingent Consideration [Line Items]
Loss Sharing Agreement Allocation Percentage			80.00%
Banco Popular De Puerto Rico [Member] | Pending Dispute With FDIC [Member]
Business Acquisition, Contingent Consideration [Line Items]
F D I C Indemnification Asset	$ 141,300,000		$ 141,300,000
Federal Deposit Insurance Corporation [Member]
Business Acquisition, Contingent Consideration [Line Items]
Loss Sharing Agreement Allocation Percentage			80.00%
Federal Deposit Insurance Corporation [Member] | Residential Mortgage
Business Acquisition, Contingent Consideration [Line Items]
Loss Sharing Term	10		10