NONINTEREST INCOME - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2018
Trust and investment services fees
Trailing commission income	$ 4	$ 8

Contract with Customer, Trailing Commission Income

No definition available.

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