Loans - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended				6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2013 Sale Non Performing Loans [Member]	Mar. 31, 2013 Sale Non Performing Loans [Member]	Jun. 30, 2014 Residential Mortgage	Jun. 30, 2013 Residential Mortgage	Jun. 30, 2014 Residential Mortgage	Jun. 30, 2013 Residential Mortgage	Jun. 30, 2014 Residential Mortgage Trading Account Assets[Member]	Jun. 30, 2013 Residential Mortgage Trading Account Assets[Member]	Jun. 30, 2014 Residential Mortgage Trading Account Assets[Member]	Jun. 30, 2013 Residential Mortgage Trading Account Assets[Member]	Jun. 30, 2014 Residential Mortgage Trading Account Assets[Member] Government National Mortgage Association Certificates And Obligations GNMA Member	Jun. 30, 2013 Residential Mortgage Trading Account Assets[Member] Government National Mortgage Association Certificates And Obligations GNMA Member	Jun. 30, 2014 Residential Mortgage Trading Account Assets[Member] Government National Mortgage Association Certificates And Obligations GNMA Member	Jun. 30, 2013 Residential Mortgage Trading Account Assets[Member] Government National Mortgage Association Certificates And Obligations GNMA Member	Jun. 30, 2014 Residential Mortgage Trading Account Assets[Member] Federal National Mortgage Association Certificates And Obligations FNMA Member	Jun. 30, 2013 Residential Mortgage Trading Account Assets[Member] Federal National Mortgage Association Certificates And Obligations FNMA Member	Jun. 30, 2014 Residential Mortgage Trading Account Assets[Member] Federal National Mortgage Association Certificates And Obligations FNMA Member	Jun. 30, 2013 Residential Mortgage Trading Account Assets[Member] Federal National Mortgage Association Certificates And Obligations FNMA Member	Jun. 30, 2014 Residential Mortgage Trading Account Assets[Member] Federal Home Loan Mortgage Corporation Certificates And Obligations FHLMC Member	Jun. 30, 2013 Residential Mortgage Trading Account Assets[Member] Federal Home Loan Mortgage Corporation Certificates And Obligations FHLMC Member	Jun. 30, 2014 Residential Mortgage Trading Account Assets[Member] Federal Home Loan Mortgage Corporation Certificates And Obligations FHLMC Member	Jun. 30, 2013 Residential Mortgage Trading Account Assets[Member] Federal Home Loan Mortgage Corporation Certificates And Obligations FHLMC Member	Jun. 30, 2014 Consumer [Member]	Jun. 30, 2013 Consumer [Member]	Jun. 30, 2014 Consumer [Member]	Jun. 30, 2013 Consumer [Member]	Jun. 30, 2014 Mortgages [Member]	Jun. 30, 2013 Mortgages [Member]	Jun. 30, 2014 Mortgages [Member]	Jun. 30, 2013 Mortgages [Member]	Jun. 30, 2014 Commercial Loans [Member]	Jun. 30, 2013 Commercial Loans [Member]	Jun. 30, 2014 Commercial Loans [Member]	Jun. 30, 2013 Commercial Loans [Member]	Jun. 30, 2014 Westernbank Puerto Rico [Member] A S C Subtopic 31020 [Member] Acquired Loans In An F D I C Assisted Transaction [Member]	Jun. 30, 2013 Westernbank Puerto Rico [Member] A S C Subtopic 31020 [Member] Acquired Loans In An F D I C Assisted Transaction [Member]	Jun. 30, 2014 Westernbank Puerto Rico [Member] Covered Under Loss Sharing Agreements With F D I C [Member] A S C Subtopic 31030 [Member] Acquired Loans In An F D I C Assisted Transaction [Member]	Dec. 31, 2013 Westernbank Puerto Rico [Member] Covered Under Loss Sharing Agreements With F D I C [Member] A S C Subtopic 31030 [Member] Acquired Loans In An F D I C Assisted Transaction [Member]	Jun. 30, 2014 SOP Non-Covered Loans [Member] A S C Subtopic 31030 [Member]	Dec. 31, 2013 SOP Non-Covered Loans [Member] A S C Subtopic 31030 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable Acquired With Deteriorated Credit Quality																																							$ 100,000,000	$ 200,000,000
Outstanding principal balance of SOP loans																																									3,400,000,000	3,800,000,000	226,000,000	197,000,000
Purchase of Loans																											0	42,000,000	92,000,000	42,000,000	169,000,000	400,000,000	331,000,000	1,500,000,000	0	3,000,000	21,000,000	3,000,000
Residential Mortgage Loans Sold					435,000,000		27,000,000	503,000,000	70,000,000	553,000,000
Commercial Construction Loans Sold	30,000,000	6,000,000	61,000,000	407,000,000		401,000,000
Transfers Of Financial Assets Accounted For As Sale Initial Fair Value Of Asset Obtained As Proceeds							$ 247,295,000	$ 437,570,000	$ 479,008,000	$ 855,707,000	$ 244,376,000	$ 432,933,000	$ 472,891,000	$ 846,327,000	$ 184,307,000	$ 282,317,000	$ 350,239,000	$ 567,569,000	$ 60,069,000	$ 123,924,000	$ 122,652,000	$ 252,066,000	$ 0	$ 26,692,000	$ 0	$ 26,692,000