PREMISES, EQUIPMENT, AND SOFTWARE - Schedule of Amortization (Details) $ in Millions	Dec. 31, 2025 USD ($)
Capitalized Software, Expected Future Amortization Expense [Abstract]
2026	$ 232
2027	176
2028	119
2029	63
2030	20
Thereafter	0
Total	610
In-process software	$ 275

- Definition

The amount of capitalized computer software amortization expense expected to be recognized after the fifth fiscal year following the latest fiscal year.

+ References

No definition available.

+ Details

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

- Definition

The amount of capitalized computer software amortization expense expected to be recognized during year five of the succeeding fiscal years.

+ References

No definition available.

+ Details

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

- Definition

The amount of capitalized computer software amortization expense expected to be recognized during year four of the succeeding fiscal years.

+ References

No definition available.

+ Details

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

- Definition

The amount of capitalized computer software amortization expense expected to be recognized during the succeeding fiscal year.

+ References

No definition available.

+ Details

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

- Definition

The amount of capitalized computer software amortization expense expected to be recognized during year three of the succeeding fiscal years.

+ References

No definition available.

+ Details

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

- Definition

The amount of capitalized computer software amortization expense expected to be recognized during year two of the succeeding fiscal years.

+ References

No definition available.

+ Details

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

- Definition

The amount of capitalized computer software amortization expense to be recognized.

+ References

No definition available.

+ Details

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

- Definition

Capitalized Software Development Costs For Internal Use Software

+ References

No definition available.

+ Details

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

- Definition

Capitalized Software, Expected Future Amortization Expense [Abstract]

+ References

No definition available.

+ Details

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