BORROWED FUNDS - Long Term Debt (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2015	Jul. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term borrowed funds		$ 4,153		$ 4,642
Derivative		(1,010)		(790)
Hedge of interest rate risk
Debt Instrument [Line Items]
Derivative		(837)		(613)
Subordinated Debt | 4.350% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Interest rate			4.35%
Subordinated Debt | Citizens Financial Group, Inc. | 4.150% fixed rate subordinated debt, due 2022
Debt Instrument [Line Items]
Long-term borrowed funds		$ 350		350
Interest rate		4.15%
Maturity date		Sep. 28, 2022
Subordinated Debt | Citizens Financial Group, Inc. | 5.158% fixed-to-floating rate subordinated debt, (LIBOR 3.56%) callable, due 2023
Debt Instrument [Line Items]
Long-term borrowed funds	[1]	$ 333		333
Interest rate	[1]	5.158%
Maturity date	[1]	Jun. 30, 2023
Subordinated Debt | Citizens Financial Group, Inc. | 5.158% fixed-to-floating rate subordinated debt, (LIBOR 3.56%) callable, due 2023 | LIBOR
Debt Instrument [Line Items]
Interest rate	[1]	3.56%
Subordinated Debt | Citizens Financial Group, Inc. | 4.771% fixed rate subordinated debt, due 2023
Debt Instrument [Line Items]
Long-term borrowed funds	[1]	$ 333		333
Interest rate	[1]	4.771%
Maturity date	[1]	Oct. 31, 2023
Subordinated Debt | Citizens Financial Group, Inc. | 4.691% fixed rate subordinated debt, due 2024
Debt Instrument [Line Items]
Long-term borrowed funds	[1]	$ 334		334
Interest rate	[1]	4.691%
Maturity date	[1]	Jan. 31, 2024
Subordinated Debt | Citizens Financial Group, Inc. | 4.153% fixed rate subordinated debt due 2024
Debt Instrument [Line Items]
Long-term borrowed funds	[1]	$ 333		333
Interest rate	[1]	4.153%
Maturity date	[1]	Jul. 31, 2024
Subordinated Debt | Citizens Financial Group, Inc. | 4.023% fixed rate subordinated debt, due 2024
Debt Instrument [Line Items]
Long-term borrowed funds	[1]	$ 333		333
Interest rate	[1]	4.023%
Maturity date	[1]	Oct. 31, 2024
Subordinated Debt | Citizens Financial Group, Inc. | 4.082% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Long-term borrowed funds	[1]	$ 334		334
Interest rate	[1]	4.082%
Maturity date	[1]	Jan. 31, 2025
Subordinated Debt | Citizens Financial Group, Inc. | 4.350% fixed rate subordinated debt, due 2025
Debt Instrument [Line Items]
Long-term borrowed funds	[1]	$ 250		0
Interest rate	[1]	4.35%
Maturity date	[1]	Aug. 01, 2025
Senior Unsecured Notes | 2.450% and 1.600% senior unsecured notes, due 2019 and 2017
Debt Instrument [Line Items]
Unsecured Debt	[2],[3]	$ 1,500
Senior Unsecured Notes | 2.450% and 1.600% senior unsecured notes, due 2019 and 2017 | Hedge of interest rate risk
Debt Instrument [Line Items]
Derivative		5		13
Senior Unsecured Notes | Banking Subsidiaries | 1.600% senior unsecured notes, due 2017
Debt Instrument [Line Items]
Long-term borrowed funds	[2],[3]	$ 755		750
Interest rate	[2],[3]	1.60%
Maturity date	[2],[3]	Dec. 04, 2017
Senior Unsecured Notes | Banking Subsidiaries | 2.450% senior unsecured notes, due 2019
Debt Instrument [Line Items]
Long-term borrowed funds	[2],[3]	$ 763		746
Interest rate	[2],[3]	2.45%
Maturity date	[2],[3]	Dec. 04, 2019
Federal Home Loan advances | Banking Subsidiaries
Debt Instrument [Line Items]
Long-term borrowed funds		$ 18		772
Maturity date		Jan. 01, 2033
Other | Banking Subsidiaries
Debt Instrument [Line Items]
Long-term borrowed funds		$ 17		$ 24

[1] Intercompany borrowed funds with RBS. See Note 14 “Related Party Transactions” for further information.

[2] $1.5 billion principal balance of unsecured notes presented net of $5 million and $13 million hedge of interest rate risk on medium term debt using interest rate swaps at September 30, 2015. See Note 12 “Derivatives” for further information.

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