SIGNIFICANT ACCOUNTING POLICIES Narrative (Details) $ in Millions	Dec. 31, 2016 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Loan analysis threshold	$ 3

Balance threshold used in determining amount of probable loss.

No definition available.

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