Note Fair value of financial instruments (Carrying or notional amounts and estimated fair values for financial instruments) (Detail) - USD ($) $ in Thousands		Jun. 30, 2018		Mar. 31, 2018	Dec. 31, 2017		Jun. 30, 2017	Dec. 31, 2016
Financial Assets:
Cash And Due From Banks		$ 400,568			$ 402,857
Money market investments		8,628,442			5,255,119
Trading account debt securities, excluding derivatives		41,637			33,926
Available For Sale Securities Debt Securities		10,542,010			10,176,923
Debt securities held-to-maturity, at amortized cost		104,937	[1]		107,019	[2]
Debt securities held-to-maturity, fair value		107,396	[1]		97,501	[2]
Equity securities:
Equity securities		159,017			165,103
FDIC loss-share asset		0			45,192
Mortgage servicing rights		164,025			168,031		$ 188,728	$ 196,889
Derivatives		15,763			16,719
Deposits
Time deposits		7,423,087			7,514,878
Total deposits		39,377,561			35,453,508
Notes payable:
Others		18,234			18,642
Notes Payable		1,561,663			1,536,356
Contingent consideration				$ 171,000	165,000
Carrying amount
Financial Assets:
Cash And Due From Banks		400,568			402,857
Money market investments		8,628,442			5,255,119
Trading account debt securities, excluding derivatives	[3]	41,637			33,746
Available For Sale Securities Debt Securities		10,542,010			10,176,923
Debt securities held-to-maturity, at amortized cost		104,937			107,019
Equity securities:
FHLB Stock		56,099			57,819
FRB stock		88,817			94,308
Other investments		14,101			12,976
Equity securities		159,017			165,103
Loans held-for-sale		73,859			132,395
Loans covered under loss sharing agreements with the FDIC					484,030
FDIC loss-share asset					45,192
Mortgage servicing rights		164,025			168,031
Derivatives		15,763			16,719
Deposits
Demand deposits		31,954,476			27,938,630
Time deposits		7,423,085			7,514,878
Total deposits		39,377,561			35,453,508
Assets sold under agreements to repurchase		306,911			390,921
Other short-term borrowings	[4]	1,200			96,208
Notes payable:
Advances with the FHLB		656,150			631,490
Senior Long Term Notes		447,915			446,873
Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust		439,364			439,351
Others		18,234			18,642
Notes Payable		1,561,663			1,536,356
Derivatives		14,223			14,431
Contingent consideration					164,858
Fair Value
Financial Assets:
Cash And Cash Equivalents Fair Value Disclosure		400,568			402,857
Money Market Investments Fair Value		8,628,442			5,255,119
Trading account debt securities, excluding derivatives		41,637			33,746
Available For Sale Securities Debt Securities		10,542,010			10,176,923
Debt securities held-to-maturity, fair value		107,396			97,501
Equity securities:
FHLB Stock		56,099			57,819
FRB stock		88,817			94,308
Other investments		18,400			16,290
Equity securities		163,316			168,417
Loans held-for-sale		74,719			134,839
F D I C Indemnification Asset Fair Value Portion					33,323
Mortgage servicing rights		164,025			168,031
Derivatives		15,763			16,719
Deposits
Demand deposits		31,954,476			27,938,630
Time deposits		7,220,074			7,381,232
Deposits		39,174,550			35,319,862
Assets sold under agreements to repurchase		306,941			390,752
Other short-term borrowings		1,200			96,208
Notes payable:
FHLB advances		649,118			628,839
Unsecured senior debt securities		460,463			463,554
Junior subordinated deferrable interest debentures		416,875			406,883
Others		18,234			18,642
Notes payable		1,544,690			1,517,918
Derivatives		14,223			14,431
Contingent consideration					164,858
Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Available For Sale Securities Debt Securities		6,643			6,609
Debt securities held-to-maturity, at amortized cost		90,928			92,754
Debt securities held-to-maturity, fair value		93,390			83,239
Obligations of Puerto Rico, States and political subdivisions | Carrying amount
Financial Assets:
Debt securities held-to-maturity, at amortized cost		90,928			92,754
Obligations of Puerto Rico, States and political subdivisions | Fair Value
Financial Assets:
Debt securities held-to-maturity, fair value		93,390			83,239
Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Available For Sale Securities Debt Securities		809,669			943,753
Debt securities held-to-maturity, at amortized cost		61			67
Debt securities held-to-maturity, fair value		65			71
Collateralized Mortgage Obligations - Federal agencies | Carrying amount
Financial Assets:
Debt securities held-to-maturity, at amortized cost		61			67
Collateralized Mortgage Obligations - Federal agencies | Fair Value
Financial Assets:
Debt securities held-to-maturity, fair value		65			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, at amortized cost		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		681			802
Debt securities held-to-maturity, at amortized cost		750			1,000
Debt securities held-to-maturity, fair value		743			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		743			993
Level 1
Financial Assets:
Cash And Cash Equivalents Fair Value Disclosure		400,568			402,857
Money Market Investments Fair Value		8,617,121			5,245,346
Trading account debt securities, excluding derivatives	[3]	4,956			261
Available For Sale Securities Debt Securities		552,388			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		0			0
Loans held-for-sale		0			0
F D I C Indemnification Asset Fair Value Portion					0
Mortgage servicing rights		0			0
Derivatives		0			0
Deposits
Demand deposits		0			0
Time deposits		0			0
Deposits		0			0
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
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		11,321			9,773
Trading account debt securities, excluding derivatives	[3]	35,462			32,384
Available For Sale Securities Debt Securities		9,988,358			9,672,250
Debt securities held-to-maturity, fair value		13,941			13,948
Equity securities:
FHLB Stock		56,099			57,819
FRB stock		88,817			94,308
Other investments		12,798			11,076
Equity securities		157,714			163,203
Loans held-for-sale		0			0
F D I C Indemnification Asset Fair Value Portion					0
Mortgage servicing rights		0			0
Derivatives		15,763			16,719
Deposits
Demand deposits		31,954,476			27,938,630
Time deposits		7,220,074			7,381,232
Deposits		39,174,550			35,319,862
Assets sold under agreements to repurchase		306,941			390,752
Other short-term borrowings	[4]	1,200			96,208
Notes payable:
FHLB advances		649,118			628,839
Unsecured senior debt securities		460,463			463,554
Junior subordinated deferrable interest debentures		416,875			406,883
Others		0			0
Notes payable		1,526,456			1,499,276
Derivatives		14,223			14,431
Contingent consideration					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		743			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]	1,219			1,101
Available For Sale Securities Debt Securities		1,264			1,288
Debt securities held-to-maturity, fair value		93,455			83,553
Equity securities:
FHLB Stock		0			0
FRB stock		0			0
Other investments		5,602			5,214
Equity securities		5,602			5,214
Loans held-for-sale		74,719			134,839
F D I C Indemnification Asset Fair Value Portion					33,323
Mortgage servicing rights		164,025			168,031
Derivatives		0			0
Deposits
Demand deposits		0			0
Time deposits		0			0
Deposits		0			0
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		18,234			18,642
Notes payable		18,234			18,642
Derivatives		0			0
Contingent consideration					164,858
Level 3 | Obligations of Puerto Rico, States and political subdivisions
Financial Assets:
Debt securities held-to-maturity, fair value		93,390			83,239
Level 3 | Collateralized Mortgage Obligations - Federal agencies
Financial Assets:
Debt securities held-to-maturity, fair value		65			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		23,965,498			23,702,612
Non-covered loans | Fair Value
Equity securities:
Loans Receivable, Fair Value Disclosure		21,825,495			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		$ 21,825,495			21,883,003
Covered loans | Fair Value
Equity securities:
Loans Receivable, Fair Value Disclosure					465,893
Covered loans | Level 1
Equity securities:
Loans Receivable, Fair Value Disclosure					0
Covered loans | Level 2
Equity securities:
Loans Receivable, Fair Value Disclosure					0
Covered loans | Level 3
Equity securities:
Loans Receivable, Fair Value Disclosure					$ 465,893

[1] Includes $90.9 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.