BORROWED FUNDS - Long Term Debt (Details) - USD ($) $ in Millions		Mar. 07, 2016	Mar. 31, 2016		Dec. 31, 2015	Aug. 03, 2015
Debt Instrument [Line Items]
Long-term borrowed funds			$ 10,035		$ 9,886
Interest rate swaps			(1,192)		(807)
Interest rate swaps
Debt Instrument [Line Items]
Interest rate swaps			(1,035)		(636)
Subordinated Debt | 4.350% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Interest rate						4.35%
Citizens Financial Group, Inc.
Debt Instrument [Line Items]
Long-term borrowed funds			2,487
Citizens Financial Group, Inc. | Subordinated Debt | 4.150% fixed rate subordinated debt, due 2022
Debt Instrument [Line Items]
Long-term borrowed funds	[1]		$ 347		350
Interest rate	[1]		4.15%
Principal balance			$ 350		350
Unamortized deferred issuance costs and discount			(3)
Citizens Financial Group, Inc. | Subordinated Debt | 5.158% fixed-to-floating rate subordinated debt, (LIBOR 3.56%) callable, due 2023
Debt Instrument [Line Items]
Long-term borrowed funds	[2]		$ 333		333
Interest rate	[2]		5.158%
Citizens Financial Group, Inc. | Subordinated Debt | 3.750% fixed rate subordinated debt due 2024
Debt Instrument [Line Items]
Long-term borrowed funds	[2],[3]		$ 250		$ 250
Interest rate	[2]		3.75%	[3]	4.153%
Citizens Financial Group, Inc. | Subordinated Debt | 4.023% fixed rate subordinated debt, due 2024
Debt Instrument [Line Items]
Long-term borrowed funds	[2],[4]		$ 214		$ 331
Interest rate	[2],[4]		4.023%
Principal balance			$ 208		333
Extinguishment of debt, amount		$ 125
Citizens Financial Group, Inc. | Subordinated Debt | 4.082% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Long-term borrowed funds	[2],[5]		$ 346		331
Interest rate	[2],[5]		4.082%
Principal balance			$ 334		334
Citizens Financial Group, Inc. | Subordinated Debt | 4.350% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Long-term borrowed funds	[6]		$ 248		250
Interest rate	[6]		4.35%
Principal balance			$ 250		250
Unamortized deferred issuance costs and discount			(2)
Citizens Financial Group, Inc. | Subordinated Debt | 4.300% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Long-term borrowed funds	[7]		$ 749		750
Interest rate	[7]		4.30%
Principal balance			$ 750		750
Unamortized deferred issuance costs and discount			$ (1)
Citizens Financial Group, Inc. | Subordinated Debt | LIBOR | 5.158% fixed-to-floating rate subordinated debt, (LIBOR 3.56%) callable, due 2023
Debt Instrument [Line Items]
Interest rate	[2]		3.56%
Citizens Financial Group, Inc. | Senior Unsecured Notes | Interest rate swaps | 4.023% fixed rate subordinated debt, due 2024
Debt Instrument [Line Items]
Interest rate swaps			$ 6		(2)
Citizens Financial Group, Inc. | Senior Unsecured Notes | Interest rate swaps | 4.082% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Interest rate swaps			12		(3)
Banking Subsidiaries
Debt Instrument [Line Items]
Long-term borrowed funds			7,548
Banking Subsidiaries | Senior Unsecured Notes | 1.600% senior unsecured notes, due 2017
Debt Instrument [Line Items]
Long-term borrowed funds	[8],[9]		$ 752		749
Interest rate	[8],[9]		1.60%
Principal balance			$ 750		750
Unamortized deferred issuance costs and discount			(1)
Banking Subsidiaries | Senior Unsecured Notes | 2.300% senior unsecured notes, due 2018
Debt Instrument [Line Items]
Long-term borrowed funds	[9],[10]		$ 753		747
Interest rate	[9],[10]		2.30%
Principal balance			$ 750		750
Unamortized deferred issuance costs and discount			(3)
Banking Subsidiaries | Senior Unsecured Notes | 2.450% senior unsecured notes, due 2019
Debt Instrument [Line Items]
Long-term borrowed funds	[9],[11]		$ 763		752
Interest rate	[9],[11]		2.45%
Principal balance			$ 750		750
Unamortized deferred issuance costs and discount			(3)
Banking Subsidiaries | Senior Unsecured Notes | 2.500% senior unsecured notes, due 2019
Debt Instrument [Line Items]
Long-term borrowed funds	[9],[12]		$ 750		0
Interest rate	[9],[12]		2.50%
Principal balance			$ 750
Unamortized deferred issuance costs and discount			(2)
Banking Subsidiaries | Senior Unsecured Notes | Interest rate swaps | 1.600% senior unsecured notes, due 2017
Debt Instrument [Line Items]
Interest rate swaps			3		(1)
Banking Subsidiaries | Senior Unsecured Notes | Interest rate swaps | 2.300% senior unsecured notes, due 2018
Debt Instrument [Line Items]
Interest rate swaps			6		(3)
Banking Subsidiaries | Senior Unsecured Notes | Interest rate swaps | 2.450% senior unsecured notes, due 2019
Debt Instrument [Line Items]
Interest rate swaps			16		2
Banking Subsidiaries | Senior Unsecured Notes | Interest rate swaps | 2.500% senior unsecured notes, due 2019
Debt Instrument [Line Items]
Interest rate swaps			2
Banking Subsidiaries | Federal Home Loan advances
Debt Instrument [Line Items]
Long-term borrowed funds			4,516		5,018
Banking Subsidiaries | Other
Debt Instrument [Line Items]
Long-term borrowed funds			$ 14		$ 25

[1] These balances are comprised of: principal balances of $350 million at March 31, 2016 and December 31, 2015, as well as the impact of ($3) million of unamortized deferred issuance costs and discount at March 31, 2016.

[2] Borrowed funds with RBS. See Note 13 “Related Party Transactions and Significant Transactions with RBS” for further information.

[3] Prior to January 1, 2016, interest was payable at a fixed rate per annum of 4.153%.

[4] These balances are comprised of: principal balance of $208 million and $333 million at March 31, 2016 and December 31, 2015, respectively, as well as the impact from interest rate swaps of $6 million and ($2) million at March 31, 2016 and December 31, 2015, respectively. See Note 11 “Derivatives” for further information. In addition, on March 7, 2016, the Company repurchased $125 million of these securities from RBS. See Note 13 “Related Party Transactions and Significant Transactions with RBS” for further information.

[5] These balances are comprised of: principal balance of $334 million at March 31, 2016 and December 31, 2015; impact from interest rate swaps of $12 million and ($3) million at March 31, 2016 and December 31, 2015, respectively. See Note 11 “Derivatives” for further information.

[6] These balances are comprised of: principal balances of $250 million at March 31, 2016 and December 31, 2015, as well as the impact of ($2) million of unamortized deferred issuance costs and discount at March 31, 2016.

[7] These balances are comprised of: principal balances of $750 million at March 31, 2016 and December 31, 2015, as well as the impact of ($1) million of unamortized deferred issuance costs and discount at March 31, 2016.

[8] These balances are comprised of: principal balances of $750 million at March 31, 2016 and December 31, 2015; impact from interest rate swaps of $3 million and ($1) million at March 31, 2016 and December 31, 2015, respectively; and ($1) million of unamortized deferred issuance costs and discount at March 31, 2016. See Note 11 “Derivatives” for further information.

[9] These securities were offered under CBNA’s Global Bank Note Program dated December 1, 2014.

[10] These balances are comprised of: principal balances of $750 million at March 31, 2016 and December 31, 2015; impact from interest rate swaps of $6 million and ($3) million at March 31, 2016 and December 31, 2015, respectively; and ($3) million of unamortized deferred issuance costs and discount at March 31, 2016. See Note 11 “Derivatives” for further information.

[11] These balances are comprised of: principal balances of $750 million at March 31, 2016 and December 31, 2015; impact from interest rate swaps of $16 million and $2 million at March 31, 2016 and December 31, 2015, respectively; and ($3) million of unamortized deferred issuance costs and discount at March 31, 2016. See Note 11 “Derivatives” for further information.

[12] The balance is comprised of: principal balance of $750 million at March 31, 2016; impact from interest rate swaps of $2 million and $(2) million of unamortized deferred issuance costs and discount at March 31, 2016. See Note 11 “Derivatives” for further information.