Note Allowance for loan losses (Allowance Movement) (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		$ 540,651		$ 537,111
Provision for loan losses		40,698		44,835
Charge-offs		(59,068)		(59,937)
Recoveries		22,215		16,463
Balance at end of period		544,496		538,472
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		118,072		124,037
General ALLL		426,424		414,435
Ending balance: loans individually evaluated for impairment		970,210		934,650
Ending balance: loans collectively evaluated for impairment		22,316,491		22,198,217
Non-covered Loans held-in-portfolio		22,734,721	[1],[2]		$ 22,773,747	[3],[4]
Loans covered under loss-sharing agreements with the FDIC		551,980			572,878
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		23,286,701		23,132,867
Covered loans
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Loans covered under loss-sharing agreements with the FDIC		551,980	[5]		572,878	[6]
PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	[7]	16,976,229			17,168,424
PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		467,984		469,923
Provision for loan losses		31,478		43,871
Charge-offs		(52,794)		(54,990)
Recoveries		19,849		14,343
Balance at end of period		466,517		473,147
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		115,196		121,864
General ALLL		351,321		351,283
Ending balance: loans individually evaluated for impairment		958,509		924,494
Ending balance: loans collectively evaluated for impairment		16,017,720		16,600,933
Non-covered Loans held-in-portfolio		16,976,229		17,525,427
PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		30,350		34,176
Provision for loan losses		(1,359)		(3,105)
Charge-offs		(1,324)		(1,254)
Recoveries		104		228
Balance at end of period		27,771		30,045
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		27,771		30,045
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		551,980		625,130
Loans covered under loss-sharing agreements with the FDIC		551,980		625,130
UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio		5,758,492			5,605,323
UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		42,317		33,012
Provision for loan losses		10,579		4,069
Charge-offs		(4,950)		(3,693)
Recoveries		2,262		1,892
Balance at end of period		50,208		35,280
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		2,876		2,173
General ALLL		47,332		33,107
Ending balance: loans individually evaluated for impairment		11,701		10,156
Ending balance: loans collectively evaluated for impairment		5,746,791		4,972,154
Non-covered Loans held-in-portfolio		5,758,492		4,982,310
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		202,654		196,833
Provision for loan losses		8,205		13,253
Charge-offs		(11,141)		(9,463)
Recoveries		8,966		6,554
Balance at end of period		208,684		207,177
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		51,276		55,098
General ALLL		157,408		152,079
Ending balance: loans individually evaluated for impairment		348,823		338,980
Ending balance: loans collectively evaluated for impairment		10,462,877		9,889,409
Non-covered Loans held-in-portfolio		10,811,700			10,798,507
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		10,811,700		10,228,389
Commercial | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	[7]	7,064,330			7,202,217
Commercial | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		189,686		186,925
Provision for loan losses		583		13,369
Charge-offs		(11,071)		(8,968)
Recoveries		8,433		6,264
Balance at end of period		187,631		197,590
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		51,276		55,098
General ALLL		136,355		142,492
Ending balance: loans individually evaluated for impairment		348,823		338,980
Ending balance: loans collectively evaluated for impairment		6,715,507		7,029,311
Non-covered Loans held-in-portfolio		7,064,330		7,368,291
Commercial | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		0		0
Provision for loan losses		0		0
Charge-offs		0		0
Recoveries		0		0
Balance at end of period		0		0
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		0		0
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		0		0
Loans covered under loss-sharing agreements with the FDIC		0		0
Commercial | UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio		3,747,370			3,596,290
Commercial | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		12,968		9,908
Provision for loan losses		7,622		(116)
Charge-offs		(70)		(495)
Recoveries		533		290
Balance at end of period		21,053		9,587
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		21,053		9,587
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		3,747,370		2,860,098
Non-covered Loans held-in-portfolio		3,747,370		2,860,098
Construction
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		9,525		8,869
Provision for loan losses		328		418
Charge-offs		(3,587)		(544)
Recoveries		3,731		233
Balance at end of period		9,997		8,976
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		172
General ALLL		9,997		8,804
Ending balance: loans individually evaluated for impairment		0		2,020
Ending balance: loans collectively evaluated for impairment		831,305		732,838
Non-covered Loans held-in-portfolio		831,305			776,300
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		831,305		734,858
Construction | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio		95,459			85,558
Construction | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		1,353		4,957
Provision for loan losses		464		(409)
Charge-offs		(3,587)		(544)
Recoveries		3,731		233
Balance at end of period		1,961		4,237
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		172
General ALLL		1,961		4,065
Ending balance: loans individually evaluated for impairment		0		2,020
Ending balance: loans collectively evaluated for impairment		95,459		103,124
Non-covered Loans held-in-portfolio		95,459		105,144
Construction | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		0		0
Provision for loan losses		0		0
Charge-offs		0		0
Recoveries		0		0
Balance at end of period		0		0
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		0		0
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		0		0
Loans covered under loss-sharing agreements with the FDIC		0		0
Construction | UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio		735,846			690,742
Construction | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		8,172		3,912
Provision for loan losses		(136)		827
Charge-offs		0		0
Recoveries		0		0
Balance at end of period		8,036		4,739
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		8,036		4,739
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		735,846		629,714
Non-covered Loans held-in-portfolio		735,846		629,714
Mortgages
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		178,093		167,279
Provision for loan losses		13,046		8,064
Charge-offs		(16,320)		(17,634)
Recoveries		1,741		1,712
Balance at end of period		176,560		159,421
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		43,264		43,252
General ALLL		133,296		116,169
Ending balance: loans individually evaluated for impairment		510,568		479,092
Ending balance: loans collectively evaluated for impairment		6,653,706		7,106,820
Non-covered Loans held-in-portfolio		6,627,987			6,696,361
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		7,164,274		7,585,912
Mortgages | Covered loans
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Loans covered under loss-sharing agreements with the FDIC		536,287			556,570
Mortgages | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	[7]	5,869,718			5,916,500
Mortgages | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		143,320		128,327
Provision for loan losses		15,172		10,869
Charge-offs		(14,983)		(15,972)
Recoveries		1,428		1,276
Balance at end of period		144,937		124,500
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		41,067		41,660
General ALLL		103,870		82,840
Ending balance: loans individually evaluated for impairment		501,647		471,183
Ending balance: loans collectively evaluated for impairment		5,368,071		5,628,576
Non-covered Loans held-in-portfolio		5,869,718		6,099,759
Mortgages | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		30,159		33,967
Provision for loan losses		(1,690)		(3,149)
Charge-offs		(1,231)		(1,221)
Recoveries		103		225
Balance at end of period		27,341		29,822
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		27,341		29,822
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		536,287		606,711
Loans covered under loss-sharing agreements with the FDIC		536,287		606,711
Mortgages | UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio		758,269			779,861
Mortgages | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		4,614		4,985
Provision for loan losses		(436)		344
Charge-offs		(106)		(441)
Recoveries		210		211
Balance at end of period		4,282		5,099
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		2,197		1,592
General ALLL		2,085		3,507
Ending balance: loans individually evaluated for impairment		8,921		7,909
Ending balance: loans collectively evaluated for impairment		749,348		871,533
Non-covered Loans held-in-portfolio		758,269		879,442
Legacy
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		1,343		2,687
Provision for loan losses		(665)		(450)
Charge-offs		(41)		(109)
Recoveries		529		356
Balance at end of period		1,166		2,484
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		1,166		2,484
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		40,688		61,044
Non-covered Loans held-in-portfolio	[8]	40,688			45,293
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		40,688		61,044
Legacy | UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio		40,688			45,293
Legacy | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		1,343		2,687
Provision for loan losses		(665)		(450)
Charge-offs		(41)		(109)
Recoveries		529		356
Balance at end of period		1,166		2,484
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		1,166		2,484
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		40,688		61,044
Non-covered Loans held-in-portfolio		40,688		61,044
Leasing
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		7,662		10,993
Provision for loan losses		1,048		1,680
Charge-offs		(1,341)		(2,127)
Recoveries		528		489
Balance at end of period		7,897		11,035
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		522		608
General ALLL		7,375		10,427
Ending balance: loans individually evaluated for impairment		1,803		2,391
Ending balance: loans collectively evaluated for impairment		717,840		640,751
Non-covered Loans held-in-portfolio		719,643			702,893
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		719,643		643,142
Leasing | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	[7]	719,643			702,893
Leasing | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		7,662		10,993
Provision for loan losses		1,048		1,680
Charge-offs		(1,341)		(2,127)
Recoveries		528		489
Balance at end of period		7,897		11,035
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		522		608
General ALLL		7,375		10,427
Ending balance: loans individually evaluated for impairment		1,803		2,391
Ending balance: loans collectively evaluated for impairment		717,840		640,751
Non-covered Loans held-in-portfolio		719,643		643,142
Leasing | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		0		0
Provision for loan losses		0		0
Charge-offs		0		0
Recoveries		0		0
Balance at end of period		0		0
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		0		0
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		0		0
Loans covered under loss-sharing agreements with the FDIC		0		0
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		141,374		150,450
Provision for loan losses		18,736		21,870
Charge-offs		(26,638)		(30,060)
Recoveries		6,720		7,119
Balance at end of period		140,192		149,379
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		23,010		24,907
General ALLL		117,182		124,472
Ending balance: loans individually evaluated for impairment		109,016		112,167
Ending balance: loans collectively evaluated for impairment		3,610,075		3,767,355
Non-covered Loans held-in-portfolio		3,703,398			3,754,393
Loans And Leases Receivable Covered And Not Covered Total Net Of Unearned Income		3,719,091		3,879,522
Consumer | Covered loans
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Loans covered under loss-sharing agreements with the FDIC		15,693			16,308
Consumer | PUERTO RICO
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio	[7]	3,227,079			3,261,256
Consumer | PUERTO RICO | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		125,963		138,721
Provision for loan losses		14,211		18,362
Charge-offs		(21,812)		(27,379)
Recoveries		5,729		6,081
Balance at end of period		124,091		135,785
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		22,331		24,326
General ALLL		101,760		111,459
Ending balance: loans individually evaluated for impairment		106,236		109,920
Ending balance: loans collectively evaluated for impairment		3,120,843		3,199,171
Non-covered Loans held-in-portfolio		3,227,079		3,309,091
Consumer | PUERTO RICO | Covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		191		209
Provision for loan losses		331		44
Charge-offs		(93)		(33)
Recoveries		1		3
Balance at end of period		430		223
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		0		0
General ALLL		430		223
Ending balance: loans individually evaluated for impairment		0		0
Ending balance: loans collectively evaluated for impairment		15,693		18,419
Loans covered under loss-sharing agreements with the FDIC		15,693		18,419
Consumer | UNITED STATES
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Non-covered Loans held-in-portfolio		476,319			$ 493,137
Consumer | UNITED STATES | Non-covered loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Balance at beginning of period		15,220		11,520
Provision for loan losses		4,194		3,464
Charge-offs		(4,733)		(2,648)
Recoveries		990		1,035
Balance at end of period		15,671		13,371
Financing Receivable Allowance For Credit Loss Additional Information Abstract
Specific ALLL		679		581
General ALLL		14,992		12,790
Ending balance: loans individually evaluated for impairment		2,780		2,247
Ending balance: loans collectively evaluated for impairment		473,539		549,765
Non-covered Loans held-in-portfolio		$ 476,319		$ 552,012

[1] Includes $7.3 billion pledged to secure credit facilities and public funds that the secured parties are not permitted to sell or repledge the collateral, of which $4.5 billion were pledged at the Federal Home Loan Bank("FHLB") as collateral for borrowings, $2.3 billion at the Federal Reserve Bank ("FRB") for discount window borrowings and $0.5 billion serve as collateral for public funds.

[2] Non-covered loans held-in-portfolio are net of $124 million in unearned income and exclude $85 million in loans held-for-sale.

[3] Includes $7.3 billion pledged to secure credit facilities and public funds that the secured parties are not permitted to sell or repledge the collateral, of which $4.5 billion were pledged at the FHLB as collateral for borrowings, $2.3 billion at the FRB for discount window borrowings and $0.5 billion serve as collateral for public funds.

[4] Non-covered loans held-in-portfolio are net of $121 million in unearned income and exclude $89 million in loans held-for-sale.

[5] Includes $325 million pledged to secure credit facilities at the FHLB which are not permitted to sell or repledge the collateral.

[6] Includes $337 million pledged to secure credit facilities at the FHLB which are not permitted to sell or repledge the collateral.

[7] Excludes covered loans acquired in the Westernbank FDIC-assisted transaction.

[8] The legacy portfolio is comprised of commercial loans, construction loans and lease financings related to certain lending products exited by the Corporation as part of restructuring efforts carried out in prior years at the BPNA segment.