Name:	cfg_CommitmentsAbstract
Namespace Prefix:	cfg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Name:	cfg_ConsumerProductsAbstract
Namespace Prefix:	cfg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow for indemnification payment requests during the period.

+ References

No definition available.

+ Details

Name:	cfg_IndemnificationPaymentRequestsAmountPaid
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of indemnification payment requests received during the period.

+ References

No definition available.

+ Details

Name:	cfg_IndemnificationPaymentRequestsReceivedAmount
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	cfg_LettersofCreditAbstract
Namespace Prefix:	cfg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of restitution awarded to (against) the entity in respect of litigation.

+ References

No definition available.

+ Details

Name:	cfg_LitigationSettlementRestitutionAmount
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The repurchase of loans that are secured with real estate mortgages per the terms of the original mortgage sale to government-sponsored entities and other parties.

+ References

No definition available.

+ Details

Name:	cfg_MortgageLoansRepurchased
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	cfg_MortgageRepurchaseDemandsAbstract
Namespace Prefix:	cfg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of mortgage repurchase demands received during the period.

+ References

No definition available.

+ Details

Name:	cfg_MortgageRepurchaseDemandsReceivedAmount
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for mortgage repurchase demands paid during the period.

+ References

No definition available.

+ Details

Name:	cfg_PaymentsforRepurchaseofMortgageLoans
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for acquisition of naming rights during the period.

+ References

No definition available.

+ Details

Name:	cfg_PaymentstoAcquireStadiumNamingRights
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Minimum amount of purchase arrangement maturing in the second fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

+ References

No definition available.

+ Details

Name:	cfg_PurchaseObligationDueafterNextTwelveMonths
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of credit exposure pertaining to risk participation agreements.

+ References

No definition available.

+ Details

Name:	cfg_RiskParticipationAgreements
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	cfg_RiskParticipationAgreementsAbstract
Namespace Prefix:	cfg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Average period covered by risk participation contracts in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	cfg_RiskParticipationAgreementsAverageTerm
Namespace Prefix:	cfg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of risk participation agreement counterparties.

+ References

No definition available.

+ Details

Name:	cfg_RiskParticipationAgreementsCounterpartiesNumber
Namespace Prefix:	cfg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum period covered by risk participation contracts in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	cfg_RiskParticipationAgreementsMaximumTerm
Namespace Prefix:	cfg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The total remaining amount of the contingent obligation under naming rights agreement outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	cfg_StadiumNamingRightsRemainingObligationDue
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The face amount of commercial and commercial real estate loans committed to purchase, but unsettled as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	cfg_UnsettledReceivableHeldForSaleAmount
Namespace Prefix:	cfg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of judgment or settlement awarded to (against) the entity in respect of litigation.

+ References

No definition available.

+ Details

Name:	us-gaap_LitigationSettlementAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Period covered by the long-term purchase commitment, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_LongtermPurchaseCommitmentPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum amount of purchase arrangement maturing in the next fiscal year following the latest fiscal year. Includes, but not limited to, recorded and unrecorded purchase obligations, long-term purchase commitments, and short-term purchase commitments.

+ References

No definition available.

+ Details

Name:	us-gaap_PurchaseObligationDueInNextTwelveMonths
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_LitigationCaseAxis=cfg_ConsentOrdersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=cfg_NamingRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=us-gaap_AutomobileLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_NetAmountAtRiskByProductAndGuaranteeGuaranteeTypeAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis=us-gaap_PurchaseCommitmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

COMMITMENTS AND CONTINGENCIES - Narrative (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		75 Months Ended	1 Months Ended	12 Months Ended
	Mar. 31, 2015 counterparty	Mar. 31, 2014	Mar. 31, 2015	Apr. 30, 2013	Dec. 31, 2014	Dec. 31, 2003
Risk Participation Agreements [Abstract]
Risk participation agreements	$ 26cfg_RiskParticipationAgreements		$ 26cfg_RiskParticipationAgreements		$ 19cfg_RiskParticipationAgreements
Risk participation agreements number of counterparties	75
Risk participation agreements, Maximum term	10 years
Mortgage Repurchase Demands [Abstract]
Mortgage repurchase demands received			161
Indemnification payment requests received			99
Repurchased mortgage loans	4cfg_MortgageLoansRepurchased	10cfg_MortgageLoansRepurchased	92cfg_MortgageLoansRepurchased
Indemnification payment requests paid	0	6	33
Payments for Repurchase of Mortgage Loans	4	10
Consent Orders
Consumer Products [Abstract]
Litigation settlement amount				10
Restitution amount payable					8
Minimum
Risk Participation Agreements [Abstract]
Risk participation agreements, Average term	1 year
Maximum
Risk Participation Agreements [Abstract]
Risk participation agreements, Average term	5 years
Letter of Credit
Letters of Credit [Abstract]
Letters of credit outstanding	3		3		3
Marketing rights
Commitments [Abstract]
Commitment period						25 years
Payments made	0				0
Remaining obligation due	51		51
Automobile \| Minimum
Commitments [Abstract]
Purchase commitment, Quarterly amount, May 30, 2014 through May 30, 2015	250		250
Purchase commitment, Quarterly amount, May 30, 2015 and after	400		400
Automobile \| Maximum
Commitments [Abstract]
Purchase commitment, Quarterly amount, May 30, 2014 through May 30, 2015	600		600
Purchase commitment, Quarterly amount, May 30, 2015 and after	600		600
Purchase Commitment \| Commercial real estate loans held for sale
Commitments [Abstract]
Unsettled commercial loan trades	$ 55		$ 55		$ 40