Minimum qualifying carrying balance of commercial loans.

No definition available.

Name:	cfg_CommercialLoansLargeBalanceMinimumQualifyingBalance
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

An entity's internal risk assessment as having high risk defined as certain loans with outstanding balances exceeding a percentage of the value of underlying collateral.

+ References

No definition available.

+ Details

Name:	cfg_CreditRiskHighLoantoValueLoansPercentExceedingValueOfUnderlyingCollateral
Namespace Prefix:	cfg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Recorded investment in non performing assets receivable net of valuation allowance as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	cfg_ImpairedFinancingReceivableNetofValuationAllowance
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Recorded investment in financing receivables that are on nonaccrual status and are collateralized by land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	cfg_MortgageloanscollateralizedbyOREO
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Amount of expense related to estimated loss from loan and lease transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

+ Details

Name:	us-gaap_ProvisionForLoanAndLeaseLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=us-gaap_AllowanceForLoanAndLeaseLossesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

ALLOWANCE FOR CREDIT LOSSES, NONPERFORMING ASSETS, AND CONCENTRATIONS OF CREDIT RISK - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Provision charged to income			$ 241	$ 238
Nonperforming assets, net of valuation allowance	$ 31		31		$ 36
Mortgage loans collateralized by OREO	174		174		181
Larger balance commercial loans minimum balance (greater than)	3		$ 3
High loan to value criteria (exceeds)			90.00%
Allowance for loan and lease losses
Financing Receivable, Modifications [Line Items]
Provision charged to income	75	$ 70	$ 238	215
Allowance for loan and lease losses \| Commercial
Financing Receivable, Modifications [Line Items]
Provision charged to income	$ 8	$ 24	$ 47	$ 8
Scenario, Adjustment \| Allowance for loan and lease losses \| Commercial
Financing Receivable, Modifications [Line Items]
Provision charged to income					$ 50