Federal funds purchased and repurchase Agreements (Detail) - USD ($)	Jun. 30, 2015	Dec. 31, 2014
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	$ 1,121,244,000	$ 1,171,657,000
Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	1,121,244,000	1,171,657,000
US Treasury Securities [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	999,000	0
US Treasury Securities [Member] | Maturity up to 30 days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	999,000	0
Obligations of U.S. Government sponsored entities | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	425,127,000	735,482,000
Obligations of U.S. Government sponsored entities | Maturity Overnight Member | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	275,000	0
Obligations of U.S. Government sponsored entities | Maturity up to 30 days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	65,476,000	289,545,000
Obligations of U.S. Government sponsored entities | Maturity 30 to 90 Days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	208,855,000	25,761,000
Obligations of U.S. Government sponsored entities | Maturity over 90 days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	150,521,000	420,176,000
Puerto Rico States And Political Subdivisions Debt Securities [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	6,952,000	28,596,000
Puerto Rico States And Political Subdivisions Debt Securities [Member] | Maturity Overnight Member | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	0	23,397,000
Puerto Rico States And Political Subdivisions Debt Securities [Member] | Maturity up to 30 days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	6,836,000	5,199,000
Puerto Rico States And Political Subdivisions Debt Securities [Member] | Maturity 30 to 90 Days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	116,000	0
Mortgage Backed Securities Member | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	582,585,000	254,790,000
Mortgage Backed Securities Member | Maturity Overnight Member | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	4,792,000	4,850,000
Mortgage Backed Securities Member | Maturity up to 30 days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	37,535,000	54,311,000
Mortgage Backed Securities Member | Maturity 30 to 90 Days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	70,458,000	0
Mortgage Backed Securities Member | Maturity over 90 days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	469,800,000	195,629,000
Collateralized Mortgage Obligations Member | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	103,533,000	143,319,000
Collateralized Mortgage Obligations Member | Maturity Overnight Member | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	0	0
Collateralized Mortgage Obligations Member | Maturity up to 30 days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	42,998,000	16,700,000
Collateralized Mortgage Obligations Member | Maturity 30 to 90 Days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	42,590,000	55,338,000
Collateralized Mortgage Obligations Member | Maturity over 90 days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	17,945,000	71,281,000
Other Debt Securities Member | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	2,048,000	9,470,000
Other Debt Securities Member | Maturity Overnight Member | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	1,858,000	1,353,000
Other Debt Securities Member | Maturity up to 30 days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	0	8,117,000
Other Debt Securities Member | Maturity 30 to 90 Days [Member] | Secured Debt
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	$ 190,000	$ 0