Note Fair value measurement (Assets and liabilities measured at fair value on a recurring basis) (Detail) - USD ($) $ in Thousands		Sep. 30, 2017		Dec. 31, 2016		Sep. 30, 2016	Dec. 31, 2015
Assets
Available For Sale Securities		$ 9,061,001	[1]	$ 8,209,806	[2]
Trading Securities		45,951		59,805
Mortgage servicing rights		180,157		196,889		$ 200,354	$ 211,405
Derivatives		14,234		14,094
US Treasury Securities
Assets
Available For Sale Securities		2,764,863		2,136,620
Obligations of U.S. Government sponsored entities
Assets
Available For Sale Securities		611,646		711,850
Obligations of Puerto Rico, States and political subdivisions
Assets
Available For Sale Securities		6,615		22,771
Collateralized Mortgage Obligations - Federal agencies
Assets
Available For Sale Securities		1,015,597		1,221,526
Mortgage Backed Securities
Assets
Available For Sale Securities		4,659,526		4,105,332
Equity securities
Assets
Available For Sale Securities		1,885		2,122
Other
Assets
Available For Sale Securities		869		9,585
Level 1
Assets
Available For Sale Securities	[3]	0		0
Trading Securities	[3]	0		0
Mortgage servicing rights		0		0
Derivatives		0		0
Liabilities
Derivatives		0		0
Contingent consideration		0		0
Level 2
Assets
Available For Sale Securities	[3]	9,059,713		8,208,414
Trading Securities	[3]	44,787		53,118
Mortgage servicing rights		0		0
Derivatives		14,234		14,094
Liabilities
Derivatives		(12,841)		(12,842)
Contingent consideration		0		0
Level 3
Assets
Available For Sale Securities	[3]	1,288		1,392
Trading Securities	[3]	1,164		6,678
Mortgage servicing rights		180,157		196,889
Derivatives		0		0
Liabilities
Derivatives		0		0
Contingent consideration		(166,876)		(153,158)
Fair Value, Measurements, Recurring
Assets
Available For Sale Securities		9,061,001		8,209,806
Trading Securities		45,951		59,796
Mortgage servicing rights		180,157		196,889
Derivatives		14,234		14,094
Total		9,301,343		8,480,585
Liabilities
Derivatives		(12,841)		(12,842)
Contingent consideration		(166,876)		(153,158)
Total		(179,717)		(166,000)
Fair Value, Measurements, Recurring | US Treasury Securities
Assets
Available For Sale Securities		2,764,863		2,136,620
Fair Value, Measurements, Recurring | Obligations of U.S. Government sponsored entities
Assets
Available For Sale Securities		611,646		711,850
Fair Value, Measurements, Recurring | Obligations of Puerto Rico, States and political subdivisions
Assets
Available For Sale Securities		6,615		22,771
Trading Securities		172		1,164
Fair Value, Measurements, Recurring | Collateralized Mortgage Obligations - Federal agencies
Assets
Available For Sale Securities		1,015,597		1,221,526
Fair Value, Measurements, Recurring | Mortgage Backed Securities
Assets
Available For Sale Securities		4,659,526		4,105,332
Trading Securities		32,752		42,746
Fair Value, Measurements, Recurring | Equity securities
Assets
Available For Sale Securities		1,885		2,122
Fair Value, Measurements, Recurring | Other
Assets
Available For Sale Securities		869		9,585
Trading Securities		12,179		14,565
Fair Value, Measurements, Recurring | Collateralized Mortgage Obligations
Assets
Trading Securities		848		1,321
Fair Value, Measurements, Recurring | Level 1
Assets
Available For Sale Securities		0		0
Trading Securities		0		0
Mortgage servicing rights		0		0
Derivatives		0		0
Total		0		0
Liabilities
Derivatives		0		0
Contingent consideration		0		0
Total		0		0
Fair Value, Measurements, Recurring | Level 1 | US Treasury Securities
Assets
Available For Sale Securities		0		0
Fair Value, Measurements, Recurring | Level 1 | Obligations of U.S. Government sponsored entities
Assets
Available For Sale Securities		0		0
Fair Value, Measurements, Recurring | Level 1 | Obligations of Puerto Rico, States and political subdivisions
Assets
Available For Sale Securities		0		0
Trading Securities		0		0
Fair Value, Measurements, Recurring | Level 1 | Collateralized Mortgage Obligations - Federal agencies
Assets
Available For Sale Securities		0		0
Fair Value, Measurements, Recurring | Level 1 | Mortgage Backed Securities
Assets
Available For Sale Securities		0		0
Trading Securities		0		0
Fair Value, Measurements, Recurring | Level 1 | Equity securities
Assets
Available For Sale Securities		0		0
Fair Value, Measurements, Recurring | Level 1 | Other
Assets
Available For Sale Securities		0		0
Trading Securities		0		0
Fair Value, Measurements, Recurring | Level 1 | Collateralized Mortgage Obligations
Assets
Trading Securities		0		0
Fair Value, Measurements, Recurring | Level 2
Assets
Available For Sale Securities		9,059,713		8,208,414
Trading Securities		44,787		53,118
Mortgage servicing rights		0		0
Derivatives		14,234		14,094
Total		9,118,734		8,275,626
Liabilities
Derivatives		(12,841)		(12,842)
Contingent consideration		0		0
Total		(12,841)		(12,842)
Fair Value, Measurements, Recurring | Level 2 | US Treasury Securities
Assets
Available For Sale Securities		2,764,863		2,136,620
Fair Value, Measurements, Recurring | Level 2 | Obligations of U.S. Government sponsored entities
Assets
Available For Sale Securities		611,646		711,850
Fair Value, Measurements, Recurring | Level 2 | Obligations of Puerto Rico, States and political subdivisions
Assets
Available For Sale Securities		6,615		22,771
Trading Securities		172		1,164
Fair Value, Measurements, Recurring | Level 2 | Collateralized Mortgage Obligations - Federal agencies
Assets
Available For Sale Securities		1,015,597		1,221,526
Fair Value, Measurements, Recurring | Level 2 | Mortgage Backed Securities
Assets
Available For Sale Securities		4,658,238		4,103,940
Trading Securities		32,709		37,991
Fair Value, Measurements, Recurring | Level 2 | Equity securities
Assets
Available For Sale Securities		1,885		2,122
Fair Value, Measurements, Recurring | Level 2 | Other
Assets
Available For Sale Securities		869		9,585
Trading Securities		11,630		13,963
Fair Value, Measurements, Recurring | Level 2 | Collateralized Mortgage Obligations
Assets
Trading Securities		276		0
Fair Value, Measurements, Recurring | Level 3
Assets
Available For Sale Securities		1,288		1,392
Trading Securities		1,164		6,678
Mortgage servicing rights		180,157		196,889
Derivatives		0		0
Total		182,609		204,959
Liabilities
Derivatives		0		0
Contingent consideration		(166,876)		(153,158)
Total		(166,876)		(153,158)
Fair Value, Measurements, Recurring | Level 3 | US Treasury Securities
Assets
Available For Sale Securities		0		0
Fair Value, Measurements, Recurring | Level 3 | Obligations of U.S. Government sponsored entities
Assets
Available For Sale Securities		0		0
Fair Value, Measurements, Recurring | Level 3 | Obligations of Puerto Rico, States and political subdivisions
Assets
Available For Sale Securities		0		0
Trading Securities		0		0
Fair Value, Measurements, Recurring | Level 3 | Collateralized Mortgage Obligations - Federal agencies
Assets
Available For Sale Securities		0		0
Fair Value, Measurements, Recurring | Level 3 | Mortgage Backed Securities
Assets
Available For Sale Securities		1,288		1,392
Trading Securities		43		4,755
Fair Value, Measurements, Recurring | Level 3 | Equity securities
Assets
Available For Sale Securities		0		0
Fair Value, Measurements, Recurring | Level 3 | Other
Assets
Available For Sale Securities		0		0
Trading Securities		549		602
Fair Value, Measurements, Recurring | Level 3 | Collateralized Mortgage Obligations
Assets
Trading Securities		$ 572		$ 1,321

[1] Includes $6.7 billion pledged to secure public and trust deposits, assets sold under agreements to repurchase, credit facilities and loan servicing agreements that the secured parties are not permitted to sell or repledge the collateral, of which $5.7 billion serve as collateral for public funds.

[2] Includes $4.1 billion pledged to secure public and trust deposits, assets sold under agreements to repurchase, credit facilities and loan servicing agreements that the secured parties are not permitted to sell or repledge the collateral, of which $3.4 billion serve as collateral for public funds.

[3] Refer to Note 25 to the C onsolidated F inancial S tatements for the fair value by class of financial asset and its hierarchy level.