INVESTMENT SECURITIES - Investment assets in debt securities at amortized cost pledged as collateral (Details) - Financial assets at amortised cost, category [member] $ in Millions	Dec. 31, 2019 COP ($)
Debt securities
Disclosure of financial assets [line items]
Financial assets pledged as collateral	$ 323,954
Debt securities \| Pledged in money market operations
Disclosure of financial assets [line items]
Financial assets pledged as collateral	323,954
Securities issued by the Colombian Government \| Pledged in money market operations
Disclosure of financial assets [line items]
Financial assets pledged as collateral	$ 323,954

The amount of financial assets that the entity has pledged as collateral for liabilities or contingent liabilities, including amounts that have been reclassified in accordance with paragraph 3.2.23(a) of IFRS 9. [Refer: Contingent liabilities [member]; Financial assets]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2019-01-01
-Paragraph 14
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2019-en-r&anchor=para_14_a&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_FinancialAssetsPledgedAsCollateralForLiabilitiesOrContingentLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant