EMPLOYEE BENEFITS - Narrative (Details) (USD $)	12 Months Ended					0 Months Ended	3 Months Ended	0 Months Ended	1 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Jan. 01, 2015	Mar. 31, 2015	Sep. 01, 2014	Sep. 30, 2014	Dec. 31, 2011
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Lump Sum payments					$ 196,000,000
Reduction of defined benefit obligation					240,000,000
Settlement charge					92,000,000
Amortization of actuarial loss	10,000,000	[1]	14,000,000		38,000,000
Settlements recognized in OCI	0	[1]	0		92,000,000
Fair value of plan assets	923,000,000		1,031,000,000
Postretirement Medical Plans with Prescription Drug Benefits [Abstract]
Funded status of plan	14,000,000		27,000,000
Recognized in other comprehensive income	192,000,000	[1]	(188,000,000)		40,000,000
Postemployment Benefits
(Benefit) cost	(1,000,000)		(3,000,000)		(1,000,000)
401(k) Plan
Employer matching contribution, Percent of employees' pay	5.00%				3.00%
Employer matching contribution percentage	100.00%
Employer matching contribution, Change			2.00%
Employer contribution amount	60,000,000		70,000,000		60,000,000
Subsequent Event
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amortization of actuarial loss							15,000,000
401(k) Plan
Employer matching contribution, Percent of employees' pay						4.00%
Managed portfolio | Derivative liabilities - interest rate swaps
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	(1,000,000)
Managed portfolio | Derivative liabilities - interest rate swaps | Eurodollar futures
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets			324,000,000
Postretirement Medical Plans with Prescription Drug Benefits [Abstract]
Unrealized Gain (Loss) on Derivatives			1,000,000
Citizens Financial Group, Inc.
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlements recognized in OCI					77,000,000
RBS
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Payment made due to divestiture of portion of plans associated with affiliates	1,000,000
Qualified Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Assets transferred to Affiliate plans	129,000,000	[2]	0		0			129,000,000
Liabilities transferred to Affiliate plans	148,000,000							148,000,000
Lump Sum payments	146,000,000
Amortization of actuarial loss	9,000,000	[1]	13,000,000		35,000,000
Fair value of plan assets	923,000,000	[2]	1,031,000,000	[2]	998,000,000					1,106,000,000
Postretirement Medical Plans with Prescription Drug Benefits [Abstract]
Accumulated benefit obligation	1,093,000,000	[2]	1,026,000,000		1,185,000,000
Employer contributions	0	[2]	0		0
Estimated employer contributions in 2015	100,000,000
Discount rate used in determining actuarial present value of benefit obligation	4.125%		5.00%		4.125%
Postretirement Benefit Plan
Postretirement Medical Plans with Prescription Drug Benefits [Abstract]
Accumulated benefit obligation	14,000,000		27,000,000
Recognized in other comprehensive income	1,000,000		367,000
Employer contributions	3,000,000		3,000,000		2,000,000
Estimated employer contributions in 2015	1,000,000
Discount rate used in determining actuarial present value of benefit obligation	3.50%		4.625%
Health care cost trend rate for the next year	7.00%		7.50%
Ultimate health care cost trend rate	5.00%		5.00%
Postretirement Benefit Plan | Affiliates
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Liabilities transferred to Affiliate plans									7,000,000
Postretirement Benefit Plan | 25 or more years of service
Postretirement Medical Plans with Prescription Drug Benefits [Abstract]
Cost sharing benefit (as a percentage)	70.00%
Postretirement Benefit Plan | 15-24 years of service
Postretirement Medical Plans with Prescription Drug Benefits [Abstract]
Cost sharing benefit (as a percentage)	50.00%
Non-Qualified Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Assets transferred to Affiliate plans	0	[2]	0		0
Liabilities transferred to Affiliate plans	7,000,000							7,000,000
Amortization of actuarial loss	1,000,000	[1]	1,000,000		3,000,000
Fair value of plan assets	0	[2]	0	[2]	0					0
Postretirement Medical Plans with Prescription Drug Benefits [Abstract]
Accumulated benefit obligation	117,000,000	[2]	107,000,000		116,000,000
Employer contributions	9,000,000	[2]	8,000,000		8,000,000
Estimated employer contributions in 2015	$ 8,000,000
Discount rate used in determining actuarial present value of benefit obligation	3.875%		4.75%		4.00%

[1] Results for the period September 1, 2014 through December 31, 2014 excluded $129 million in qualified plan assets, $148 million in qualified plan liabilities and $7 million in non-qualified plan liabilities transferred to Affiliates on September 1, 2014.

[2] December 31, 2014 amounts excluded $129 million in qualified plan assets, $148 million in qualified plan liabilities and $7 million in non-qualified plan liabilities transferred to Affiliates on September 1, 2014.