Pledge Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	$ 1,658,398	$ 2,324,006
Assets Not Pledged	3,710,606	3,285,225
Investment Securities
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Assets Not Pledged	921,610	648,125
Residential Mortgage Member
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Assets Not Pledged	325,698	348,030
Commercial Loan [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Assets Not Pledged	1,152,151	1,064,923
Consumer Loan [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Assets Not Pledged	361,497	329,050
Auto and Leases Loan [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Assets Not Pledged	949,650	895,097
Investment [Member] | Investment Securities
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	230,251	703,243
Mortgage Loan [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	971,772	1,028,234
Commercial Loan [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	456,375	592,529
Securities sold under agreements to repurchase secured with cash or equivalents [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	205,484	700,498
Puerto Rico public fund deposits [Member] | Investment [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	22,948	0
Puerto Rico public fund deposits [Member] | Commercial Loan [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	150,036	209,236
Puerto Rico Cash & Money Market Fund [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	0	0
Interest Rate Swap [Member] | Investment [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	1,478	2,397
Federal Reserve Bank Credit Facilities | Commercial Loan [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	993	1,303
Bond For Trust Operation [Member] | Investment [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	341	348
Federal Home Loan Bank Advances [Member] | Mortgage Loan [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	971,772	1,028,234
Federal Home Loan Bank Advances [Member] | Commercial Loan [Member]
FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Pledged Financial Instruments Not Separately Reported Securities Pledged	$ 305,346	$ 381,990