RELATED PARTY TRANSACTIONS (Narrative) (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013	Dec. 31, 2013
Related Party Transaction [Line Items]
Interest expense	$ 17,000,000		$ 4,000,000	$ 42,000,000		$ 6,000,000
Other short-term borrowed funds	21,000,000		2,000,000	70,000,000		4,000,000
Dividends to parent — exchange transactions				(666,000,000)		(666,000,000)
Interest rate swaps | Derivatives designated as hedging instruments
Related Party Transaction [Line Items]
Notional Amount	5,000,000,000	[1]		5,000,000,000	[1]		5,500,000,000	[1]
Interest rate swaps | Derivatives not designated as hedging instruments
Related Party Transaction [Line Items]
Notional Amount	28,940,000,000	[1]		28,940,000,000	[1]		29,355,000,000	[1]
Foreign exchange contracts | Derivatives not designated as hedging instruments
Related Party Transaction [Line Items]
Notional Amount	8,278,000,000	[1]		8,278,000,000	[1]		7,771,000,000	[1]
RBS
Related Party Transaction [Line Items]
Borrowing capacity							50,000,000
Income from services and referrals net of rent income (expense)	5,000,000		7,000,000	13,000,000		19,000,000
Dividend to parent	50,000,000		50,000,000	85,000,000		145,000,000
RBS | Interest rate swaps
Related Party Transaction [Line Items]
Interest expense	1,000,000		31,000,000	22,000,000		123,000,000
Derivative revenue	5,000,000					132,000,000
Derivative expense			44,000,000	130,000,000
Minimum fixed interest rate	1.78%			1.78%			1.78%
Maximum fixed interest rate	4.30%			4.30%			5.47%
Derivative executed during period	4,000,000,000		4,000,000,000	4,000,000,000		4,000,000,000
RBS | Interest rate swaps | Derivatives designated as hedging instruments
Related Party Transaction [Line Items]
Notional Amount	5,000,000,000	[1]		5,000,000,000	[1]		5,500,000,000	[1]
RBS | Interest rate swaps | Derivatives not designated as hedging instruments
Related Party Transaction [Line Items]
Notional Amount	10,600,000,000			10,600,000,000			13,400,000,000
RBS | Foreign exchange contracts
Related Party Transaction [Line Items]
Notional Amount	5,000,000,000			5,000,000,000			4,600,000,000
Foreign exchange and trade finance fees			33,000,000			20,000,000
Foreign exchange and trade finance revenue	59,000,000			52,000,000
Executive Officers, Family Members, and Their Businesses
Related Party Transaction [Line Items]
Related party loans	126,000,000			126,000,000			78,000,000
Special Dividend | RBS
Related Party Transaction [Line Items]
Dividends to parent — exchange transactions	(333,000,000)		(333,000,000)	(666,000,000)		(666,000,000)
Line of Credit
Related Party Transaction [Line Items]
Other short-term borrowed funds						$ 0

[1] The notional or contractual amount of interest rate derivatives and foreign exchange contracts is the amount upon which interest and other payments under the contract are based. For interest rate derivatives, the notional amount is typically not exchanged. Therefore, notional amounts should not be taken as the measure of credit or market risk, as they tend to greatly overstate the true economic risk of these contracts.