Note Fair value of financial instruments (Carrying or notional amounts and estimated fair values for financial instruments) (Detail) - USD ($) $ in Thousands		Mar. 31, 2018		Dec. 31, 2017		Mar. 31, 2017	Dec. 31, 2016
Financial Assets:
Cash And Due From Banks		$ 280,077		$ 402,857
Money market investments		6,984,009		5,255,119
Trading account debt securities, excluding derivatives		42,386		33,926
Available For Sale Securities Debt Securities		10,420,589		10,176,923
Debt securities held-to-maturity, at amortized cost		104,817	[1]	107,019	[2]
Debt securities held-to-maturity, fair value		98,740	[1]	97,501	[2]
Equity securities:
Equity securities (realizable value 2018 - $169,127; 2017 - $168,417)		165,218		165,103
FDIC loss-share asset		44,469		45,192
Mortgage servicing rights		166,281		168,031		$ 193,698	$ 196,889
Derivatives		15,496		16,719
Deposits
Time deposits		7,795,243		7,514,878
Total deposits		37,134,093		35,453,508
Notes payable:
Others		18,316		18,642
Notes Payable		1,564,204		1,536,356
Carrying amount
Financial Assets:
Cash And Due From Banks		280,077		402,857
Money market investments		6,984,009		5,255,119
Trading account debt securities, excluding derivatives	[3]	42,308		33,746
Available For Sale Securities Debt Securities		10,420,589		10,176,923
Debt securities held-to-maturity, at amortized cost		104,817		107,019
Equity securities:
FHLB Stock		63,113		57,819
FRB stock		88,999		94,308
Other investments		13,106		12,976
Equity securities (realizable value 2018 - $169,127; 2017 - $168,417)		165,218		165,103
Loans held-for-sale		77,701		132,395
Loans covered under loss sharing agreements with the FDIC		481,001		484,030
FDIC loss-share asset		44,469		45,192
Mortgage servicing rights		166,281		168,031
Derivatives		15,496		16,719
Deposits
Demand deposits		29,338,850		27,938,630
Time deposits		7,795,243		7,514,878
Total deposits		37,134,093		35,453,508
Federal funds purchased and assets sold under agreements to repurchase		380,061		390,921
Other short-term borrowings	[4]	186,200		96,208
Notes payable:
Advances with the FHLB		659,137		631,490
Senior Long Term Notes		447,394		446,873
Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust		439,357		439,351
Others		18,316		18,642
Notes Payable		1,564,204		1,536,356
Derivatives		13,685		14,431
Contingent consideration		170,970		164,858
Fair Value
Financial Assets:
Cash And Cash Equivalents Fair Value Disclosure		280,077		402,857
Money Market Investments Fair Value		6,984,009		5,255,119
Trading account debt securities, excluding derivatives		42,308		33,746
Available For Sale Securities Debt Securities		10,420,589		10,176,923
Debt securities held-to-maturity, fair value		98,740		97,501
Equity securities:
FHLB Stock		63,113		57,819
FRB stock		88,999		94,308
Other investments		17,015		16,290
Equity securities (realizable value 2018 - $169,127; 2017 - $168,417)		169,127		168,417
Loans held-for-sale		78,248		134,839
F D I C Indemnification Asset Fair Value Portion		32,466		33,323
Mortgage servicing rights		166,281		168,031
Derivatives		15,496		16,719
Deposits
Demand deposits		29,338,850		27,938,630
Time deposits		7,603,836		7,381,232
Deposits		36,942,686		35,319,862
Federal funds purchased and assets sold under agreements to repurchase		380,095		390,752
Other short-term borrowings		186,200		96,208
Notes payable:
FHLB advances		653,314		628,839
Unsecured senior debt securities		464,292		463,554
Junior subordinated deferrable interest debentures		412,833		406,883
Others		18,316		18,642
Notes payable		1,548,755		1,517,918
Derivatives		13,685		14,431
Contingent consideration		170,970		164,858
Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Available For Sale Securities Debt Securities		6,612		6,609
Debt securities held-to-maturity, at amortized cost		90,803		92,754
Debt securities held-to-maturity, fair value		84,726		83,239
Obligations of Puerto Rico, States and political subdivisions | Carrying amount
Financial Assets:
Debt securities held-to-maturity, at amortized cost		90,803		92,754
Obligations of Puerto Rico, States and political subdivisions | Fair Value
Financial Assets:
Debt securities held-to-maturity, fair value		84,726		83,239
Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Available For Sale Securities Debt Securities		883,633		943,753
Debt securities held-to-maturity, at amortized cost		66		67
Debt securities held-to-maturity, fair value		70		71
Collateralized Mortgage Obligations - Federal agencies | Carrying amount
Financial Assets:
Debt securities held-to-maturity, at amortized cost		66		67
Collateralized Mortgage Obligations - Federal agencies | Fair Value
Financial Assets:
Debt securities held-to-maturity, fair value		70		71
Trust preferred securities
Financial Assets:
Debt securities held-to-maturity, at amortized cost		13,198		13,198
Debt securities held-to-maturity, fair value		13,198		13,198
Trust preferred securities | Carrying amount
Financial Assets:
Debt securities held-to-maturity, fair value		13,198		13,198
Trust preferred securities | Fair Value
Financial Assets:
Debt securities held-to-maturity, fair value		13,198		13,198
Other
Financial Assets:
Available For Sale Securities Debt Securities		754		802
Debt securities held-to-maturity, at amortized cost		750		1,000
Debt securities held-to-maturity, fair value		746		993
Other | Carrying amount
Financial Assets:
Debt securities held-to-maturity, at amortized cost		750		1,000
Other | Fair Value
Financial Assets:
Debt securities held-to-maturity, fair value		746		993
Level 1
Financial Assets:
Cash And Cash Equivalents Fair Value Disclosure		280,077		402,857
Money Market Investments Fair Value		6,974,205		5,245,346
Trading account debt securities, excluding derivatives	[3]	9,251		261
Available For Sale Securities Debt Securities		501,727		503,385
Debt securities held-to-maturity, fair value		0		0
Equity securities:
FHLB Stock		0		0
FRB stock		0		0
Other investments		0		0
Equity securities (realizable value 2018 - $169,127; 2017 - $168,417)		0		0
Loans held-for-sale		0		0
F D I C Indemnification Asset Fair Value Portion		0		0
Mortgage servicing rights		0		0
Derivatives		0		0
Deposits
Demand deposits		0		0
Time deposits		0		0
Deposits		0		0
Federal funds purchased and assets sold under agreements to repurchase		0		0
Other short-term borrowings	[4]	0		0
Notes payable:
FHLB advances		0		0
Unsecured senior debt securities		0		0
Junior subordinated deferrable interest debentures		0		0
Others		0		0
Notes payable		0		0
Derivatives		0		0
Contingent consideration		0		0
Level 1 | Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Debt securities held-to-maturity, fair value		0		0
Level 1 | Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Debt securities held-to-maturity, fair value		0		0
Level 1 | Trust preferred securities
Financial Assets:
Debt securities held-to-maturity, fair value		0		0
Level 1 | Other
Financial Assets:
Debt securities held-to-maturity, fair value		0		0
Level 2
Financial Assets:
Cash And Cash Equivalents Fair Value Disclosure		0		0
Money Market Investments Fair Value		9,804		9,773
Trading account debt securities, excluding derivatives	[3]	32,007		32,384
Available For Sale Securities Debt Securities		9,917,599		9,672,250
Debt securities held-to-maturity, fair value		13,944		13,948
Equity securities:
FHLB Stock		63,113		57,819
FRB stock		88,999		94,308
Other investments		11,747		11,076
Equity securities (realizable value 2018 - $169,127; 2017 - $168,417)		163,859		163,203
Loans held-for-sale		0		0
F D I C Indemnification Asset Fair Value Portion		0		0
Mortgage servicing rights		0		0
Derivatives		15,496		16,719
Deposits
Demand deposits		29,338,850		27,938,630
Time deposits		7,603,836		7,381,232
Deposits		36,942,686		35,319,862
Federal funds purchased and assets sold under agreements to repurchase		380,095		390,752
Other short-term borrowings	[4]	186,200		96,208
Notes payable:
FHLB advances		653,314		628,839
Unsecured senior debt securities		464,292		463,554
Junior subordinated deferrable interest debentures		412,833		406,883
Others		0		0
Notes payable		1,530,439		1,499,276
Derivatives		13,685		14,431
Contingent consideration		0		0
Level 2 | Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Debt securities held-to-maturity, fair value		0		0
Level 2 | Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Debt securities held-to-maturity, fair value		0		0
Level 2 | Trust preferred securities
Financial Assets:
Debt securities held-to-maturity, fair value		13,198		13,198
Level 2 | Other
Financial Assets:
Debt securities held-to-maturity, fair value		746		750
Level 3
Financial Assets:
Cash And Cash Equivalents Fair Value Disclosure		0		0
Money Market Investments Fair Value		0		0
Trading account debt securities, excluding derivatives	[3]	1,050		1,101
Available For Sale Securities Debt Securities		1,263		1,288
Debt securities held-to-maturity, fair value		84,796		83,553
Equity securities:
FHLB Stock		0		0
FRB stock		0		0
Other investments		5,268		5,214
Equity securities (realizable value 2018 - $169,127; 2017 - $168,417)		5,268		5,214
Loans held-for-sale		78,248		134,839
F D I C Indemnification Asset Fair Value Portion		32,466		33,323
Mortgage servicing rights		166,281		168,031
Derivatives		0		0
Deposits
Demand deposits		0		0
Time deposits		0		0
Deposits		0		0
Federal funds purchased and assets sold under agreements to repurchase		0		0
Other short-term borrowings	[4]	0		0
Notes payable:
FHLB advances		0		0
Unsecured senior debt securities		0		0
Junior subordinated deferrable interest debentures		0		0
Others		18,316		18,642
Notes payable		18,316		18,642
Derivatives		0		0
Contingent consideration		170,970		164,858
Level 3 | Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Debt securities held-to-maturity, fair value		84,726		83,239
Level 3 | Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Debt securities held-to-maturity, fair value		70		71
Level 3 | Trust preferred securities
Financial Assets:
Debt securities held-to-maturity, fair value		0		0
Level 3 | Other
Financial Assets:
Debt securities held-to-maturity, fair value		0		243
Non-covered loans | Carrying amount
Equity securities:
Loans held in portfolio, net		23,480,969		23,702,612
Non-covered loans | Fair Value
Equity securities:
Loans Receivable, Fair Value Disclosure		21,484,858		21,883,003
Non-covered loans | Level 1
Equity securities:
Loans Receivable, Fair Value Disclosure		0		0
Non-covered loans | Level 2
Equity securities:
Loans Receivable, Fair Value Disclosure		0		0
Non-covered loans | Level 3
Equity securities:
Loans Receivable, Fair Value Disclosure		21,484,858		21,883,003
Covered loans | Fair Value
Equity securities:
Loans Receivable, Fair Value Disclosure		454,706		465,893
Covered loans | Level 1
Equity securities:
Loans Receivable, Fair Value Disclosure		0		0
Covered loans | Level 2
Equity securities:
Loans Receivable, Fair Value Disclosure		0		0
Covered loans | Level 3
Equity securities:
Loans Receivable, Fair Value Disclosure		$ 454,706		$ 465,893

[1] Includes $90.8 million pledged to secure public and trust deposits that the secured parties are not permitted to sell or repledge the collateral.

[2] Includes $92.8 million pledged to secure public and trust deposits that the secured parties are not permitted to sell or repledge the collateral.

[3] Refer to Note 24 to the C onsolidated F inancial S tatements for the fair value by class of financial asset and its hierarchy level.

[4] Refer to Note 16 to the Consolidated F inancial S tatements for the composition of other short-term borrowings.