BORROWED FUNDS - Long Term Debt (Details) - USD ($) $ in Millions		Mar. 31, 2017		Dec. 31, 2016
Debt Instrument [Line Items]
Long-term borrowed funds		$ 11,780		$ 12,790
Interest rate swaps		(456)	[1]	(759)
Interest rate swaps
Debt Instrument [Line Items]
Interest rate swaps		(350)		(609)
Citizens Financial Group, Inc.
Debt Instrument [Line Items]
Long-term borrowed funds		2,318
Citizens Financial Group, Inc. | Subordinated Debt | 4.150% fixed rate subordinated debt, due 2022
Debt Instrument [Line Items]
Long-term borrowed funds	[2]	$ 347		$ 347
Interest rate		4.15%		4.15%
Principal balance		$ 350		$ 350
Unamortized deferred issuance costs and discount		(3)		(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		$ 333		$ 333
Interest rate		5.158%		5.158%
Citizens Financial Group, Inc. | Subordinated Debt | 3.750% fixed rate subordinated debt, due 2024
Debt Instrument [Line Items]
Long-term borrowed funds		$ 250		$ 250
Interest rate		3.75%		3.75%
Citizens Financial Group, Inc. | Subordinated Debt | 4.023% fixed rate subordinated debt, due 2024
Debt Instrument [Line Items]
Long-term borrowed funds		$ 42		$ 42
Interest rate		4.023%		4.023%
Citizens Financial Group, Inc. | Subordinated Debt | 4.350% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Long-term borrowed funds	[3]	$ 249		$ 249
Interest rate		4.35%		4.35%
Principal balance		$ 250		$ 250
Unamortized deferred issuance costs and discount		(1)		(1)
Citizens Financial Group, Inc. | Subordinated Debt | 4.300% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Long-term borrowed funds	[4]	$ 749		$ 749
Interest rate		4.30%		4.30%
Principal balance		$ 750		$ 750
Unamortized deferred issuance costs and discount		$ (1)		$ (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		3.56%		3.56%
Citizens Financial Group, Inc. | Senior Unsecured Notes | 2.375% fixed rate subordinated debt, due 2021
Debt Instrument [Line Items]
Long-term borrowed funds	[5]	$ 348		$ 348
Interest rate		2.375%		2.375%
Principal balance		$ 350		$ 350
Unamortized deferred issuance costs and discount		(2)		(2)
Banking Subsidiaries
Debt Instrument [Line Items]
Long-term borrowed funds		9,462
Banking Subsidiaries | Senior Unsecured Notes | 2.300% senior unsecured notes, due 2018
Debt Instrument [Line Items]
Long-term borrowed funds	[6],[7]	$ 745		$ 745
Interest rate		2.30%		2.30%
Principal balance		$ 750		$ 750
Unamortized deferred issuance costs and discount		(1)		(2)
Banking Subsidiaries | Senior Unsecured Notes | 2.450% senior unsecured notes, due 2019
Debt Instrument [Line Items]
Long-term borrowed funds	[7],[8]	$ 746		$ 747
Interest rate		2.45%		2.45%
Principal balance		$ 750		$ 750
Unamortized deferred issuance costs and discount		(2)		(3)
Banking Subsidiaries | Senior Unsecured Notes | 2.500% senior unsecured notes, due 2019
Debt Instrument [Line Items]
Long-term borrowed funds	[7],[9]	$ 740		$ 741
Interest rate		2.50%		2.50%
Principal balance		$ 750		$ 750
Unamortized deferred issuance costs and discount		(2)		(2)
Banking Subsidiaries | Senior Unsecured Notes | 2.250% senior unsecured notes, due 2020
Debt Instrument [Line Items]
Long-term borrowed funds	[7],[10]	$ 697		0
Interest rate		2.25%
Principal balance		$ 700
Unamortized deferred issuance costs and discount		(2)
Banking Subsidiaries | Senior Unsecured Notes | Floating rate senior unsecured notes, due 2020
Debt Instrument [Line Items]
Long-term borrowed funds	[7],[11]	299		0
Principal balance		300
Unamortized deferred issuance costs and discount		(1)
Banking Subsidiaries | Senior Unsecured Notes | 2.550% Senior Unsecured Notes, Due 2021
Debt Instrument [Line Items]
Long-term borrowed funds	[7],[12]	$ 964		$ 965
Interest rate		2.55%		2.55%
Principal balance		$ 1,000		$ 1,000
Unamortized deferred issuance costs and discount		(4)		(5)
Banking Subsidiaries | Senior Unsecured Notes | Interest rate swaps | 2.300% senior unsecured notes, due 2018
Debt Instrument [Line Items]
Interest rate swaps		(4)		(3)
Banking Subsidiaries | Senior Unsecured Notes | Interest rate swaps | 2.450% senior unsecured notes, due 2019
Debt Instrument [Line Items]
Interest rate swaps		(2)		0
Banking Subsidiaries | Senior Unsecured Notes | Interest rate swaps | 2.500% senior unsecured notes, due 2019
Debt Instrument [Line Items]
Interest rate swaps		(8)		(7)
Banking Subsidiaries | Senior Unsecured Notes | Interest rate swaps | 2.250% senior unsecured notes, due 2020
Debt Instrument [Line Items]
Interest rate swaps		(1)
Banking Subsidiaries | Senior Unsecured Notes | Interest rate swaps | 2.550% Senior Unsecured Notes, Due 2021
Debt Instrument [Line Items]
Interest rate swaps		(32)		(30)
Banking Subsidiaries | Federal Home Loan advances
Debt Instrument [Line Items]
Long-term borrowed funds		5,262		7,264
Banking Subsidiaries | Other
Debt Instrument [Line Items]
Long-term borrowed funds		$ 9		$ 10

[1] Amounts reflect variation margin payments that are characterized as settlement per the rules of the Company’s central counterparties effective for the quarter ended March 31, 2017.

[2] These balances are composed of: principal balances of $350 million at March 31, 2017 and December 31, 2016, as well as the impact of ($3) million of unamortized deferred issuance costs and discount at March 31, 2017 and December 31, 2016.

[3] These balances are composed of: principal balances of $250 million at March 31, 2017 and December 31, 2016, as well as the impact of ($1) million of unamortized deferred issuance costs and discount at March 31, 2017 and December 31, 2016.

[4] These balances are composed of: principal balances of $750 million at March 31, 2017 and December 31, 2016, as well as the impact of ($1) million of unamortized deferred issuance costs and discount at March 31, 2017 and December 31, 2016.

[5] These balances are composed of: principal balance of $350 million at March 31, 2017 and December 31, 2016, as well as the impact of ($2) million of unamortized deferred issuance costs and discount at March 31, 2017 and December 31, 2016.

[6] These balances are composed of: principal balances of $750 million at March 31, 2017 and December 31, 2016, respectively; impact from interest rate swaps of ($4) million and ($3) million at March 31, 2017 and December 31, 2016, respectively; and ($1) million and ($2) million of unamortized deferred issuance costs and discount at March 31, 2017 and December 31, 2016, respectively. See Note 10 “Derivatives” for further information.

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

[8] These balances are composed of: principal balances of $750 million at March 31, 2017 and December 31, 2016, respectively; impact from interest rate swaps of ($2) million and zero at March 31, 2017 and December 31, 2016, respectively; and ($2) million and $(3) million of unamortized deferred issuance costs and discount at March 31, 2017 and December 31, 2016, respectively. See Note 10 “Derivatives” for further information.

[9] These balances are composed of: principal balance of $750 million at March 31, 2017 and December 31, 2016, respectively; impact from interest rate swaps of ($8) million and $(7) million at March 31, 2017 and December 31, 2016, respectively; and ($2) million of unamortized deferred issuance costs and discount at March 31, 2017 and December 31, 2016, respectively. See Note 10 “Derivatives” for further information.

[10] This balance is composed of: principal balance of $700 million at March 31, 2017; impact from interest rate swaps of ($1) million and ($2) million of unamortized deferred issuance costs and discount at March 31, 2017. See Note 10 “Derivatives” for further information.

[11] This balance is composed of: principal balance of $300 million at March 31, 2017, as well as the impact of ($1) million of unamortized deferred issuance costs and discount at March 31, 2017.

[12] These balances are composed of: principal balance of $1.0 billion at March 31, 2017 and December 31, 2016, respectively; impact from interest rate swaps of ($32) million and ($30) million at March 31, 2017 and December 31, 2016, respectively; and ($4) million and ($5) million of unamortized deferred issuance costs and discount at March 31, 2017 and December 31, 2016, respectively. See Note 10 “Derivatives” for further information.