Investment Securities (Gains and losses by category) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - less than 12 month	$ 20	$ 127,221
Available for sale - Amortized cost - more than 12 month	835,211	567,531
Total Available for Sale Amortization cost	835,231	694,752
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale - Unrealized Loss - less than 12 month	1	436
Available for sale - Unrealized Loss - more than 12 month	14,882	13,687
Total Available for Sale Unrealized Loss	14,883	14,123
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available for sale - Fair Value - less than 12 month	19	126,785
Available-for-sale, Fair Value - more than 12 month	820,329	553,844
Total Available for Sale Fair Value	820,348	680,629
Continuous Unrealized Loss Position Amortized Cost [Abstract]
Held to Maturity - Amortized cost - more than 12 month		424,740
Held to Maturity - Amortized Cost		424,740
Held To Maturity Securities, Continuous Unrealized Loss Position Aggregate Losses [Abstract]
Held to Maturity- Unrealized Loss - more than 12 month		14,387
Held to Maturity- Unrealized Loss		14,387
Held To Maturity Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Held-to-Maturity - Fair Value - more than 12 Month		410,353
Held to Maturity - Fair Value		410,353
CMO's issued by us government sponsored agencies at loss
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - more than 12 month	62,927	66,230
Total Available for Sale Amortization cost	62,927	66,230
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale - Unrealized Loss - more than 12 month	1,538	2,166
Total Available for Sale Unrealized Loss	1,538	2,166
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available-for-sale, Fair Value - more than 12 month	61,389	64,064
Total Available for Sale Fair Value	61,389	64,064
FNMA and FHLMC [Member]
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - less than 12 month		109,772
Available for sale - Amortized cost - more than 12 month	686,773	357,955
Total Available for Sale Amortization cost	686,773	467,727
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale - Unrealized Loss - less than 12 month		348
Available for sale - Unrealized Loss - more than 12 month	12,558	8,603
Total Available for Sale Unrealized Loss	12,558	8,951
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available for sale - Fair Value - less than 12 month		109,424
Available-for-sale, Fair Value - more than 12 month	674,215	349,352
Total Available for Sale Fair Value	674,215	458,776
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - less than 12 month	20	17,126
Available for sale - Amortized cost - more than 12 month	73,290	131,044
Total Available for Sale Amortization cost	73,310	148,170
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale - Unrealized Loss - less than 12 month	1	88
Available for sale - Unrealized Loss - more than 12 month	670	2,739
Total Available for Sale Unrealized Loss	671	2,827
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available for sale - Fair Value - less than 12 month	19	17,038
Available-for-sale, Fair Value - more than 12 month	72,620	128,305
Total Available for Sale Fair Value	72,639	145,343
Obligation of US Government sponsored agencies at loss [Member]
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - more than 12 month	2,238	2,325
Total Available for Sale Amortization cost	2,238	2,325
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale - Unrealized Loss - more than 12 month	42	60
Total Available for Sale Unrealized Loss	42	60
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available-for-sale, Fair Value - more than 12 month	2,196	2,265
Total Available for Sale Fair Value	2,196	2,265
US Treasury Securities at loss
Available For Sale Securities Continuous Unrealized Loss Position Amortized Cost [Abstract]
Available for sale - Amortized cost - less than 12 month		323
Available for sale - Amortized cost - more than 12 month	9,983	9,977
Total Available for Sale Amortization cost	9,983	10,300
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available for sale - Unrealized Loss - less than 12 month		0
Available for sale - Unrealized Loss - more than 12 month	74	119
Total Available for Sale Unrealized Loss	74	119
Available For Sale Securities Continuous Unrealized Loss Position Fair Value [Abstract]
Available for sale - Fair Value - less than 12 month		323
Available-for-sale, Fair Value - more than 12 month	9,909	9,858
Total Available for Sale Fair Value	$ 9,909	$ 10,181

Amortized cost of investments in available-for-sale securities that have been in a loss position.

No definition available.

Name:	ofg_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAmortizedCost
Namespace Prefix:	ofg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	ofg_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAmortizedCostAbstract
Namespace Prefix:	ofg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost of investments in available-for-sale securities that have been in a loss position for less than twelve months.

+ References

No definition available.

+ Details

Name:	ofg_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAmortizedCost
Namespace Prefix:	ofg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	ofg_AvailableForSaleUnrealizedLossLessThan12Month
Namespace Prefix:	ofg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of unrealized loss on securities classified as available-for-sale that have been in a loss position for twelve months or longer.

+ References

No definition available.

+ Details

Name:	ofg_AvailableForSaleUnrealizedLossMoreThan12Month
Namespace Prefix:	ofg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost of investments in available-for-sale securities that have been in a loss position for more than twelve months.

+ References

No definition available.

+ Details

Name:	ofg_AvailableforsalesecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAmortizedCost
Namespace Prefix:	ofg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	ofg_ContinuousUnrealizedLossPositionAmortizedCostAbstract1Abstract
Namespace Prefix:	ofg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Held to maturity securities continuous unrealized loss position, amortized cost.

+ References

No definition available.

+ Details

Name:	ofg_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAmortizedCost
Namespace Prefix:	ofg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost of investments in held-to-maturity securities that have been in a loss position for more than twelve months.

+ References

No definition available.

+ Details

Name:	ofg_HeldtomaturitysecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerAmortizedCost
Namespace Prefix:	ofg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of unrealized loss on securities classified as available-for-sale.

+ References

No definition available.

+ Details

Name:	ofg_TotalAvailableForSaleUnrealizedLoss
Namespace Prefix:	ofg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

+ References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValueAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

+ References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

+ References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for 12 months or longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValueAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss position for 12 months or longer.

+ References

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	invest_InvestmentSecuritiesClassAxis=us-gaap_CollateralizedMortgageObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	invest_InvestmentSecuritiesClassAxis=ofg_FnmaAndFhlmcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	invest_InvestmentSecuritiesClassAxis=us-gaap_GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	invest_InvestmentSecuritiesClassAxis=us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	invest_InvestmentSecuritiesClassAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: