CASH AND DUE FROM BANKS - Narrative (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash and Cash Equivalents [Abstract]
Interest-bearing cash and due from banks	$ 2,105cfg_InterestbearingCashandDuefromBanks	$ 1,351cfg_InterestbearingCashandDuefromBanks
Interest rate on FRB balances	0.25%	0.25%	0.25%
Interest earned on FRB balances	$ 5	$ 5	$ 3

For banks and other depository institutions (including Federal Reserve Banks, if applicable): Interest-bearing cash in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet.

No definition available.

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