DISCONTINUED OPERATIONS AND SIGNIFICANT DISPOSALS - Significant Disposals (Details) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Sep. 22, 2014	Sep. 30, 2014	Dec. 31, 2014
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Assets
Cash and deposits with banks	$ 626,000,000				$ 151,000,000
Investments	1,499,000,000				0
Loans, net	9,283,000,000				544,000,000
Allowance	713,000,000				2,000,000
Goodwill	112,000,000				51,000,000
Intangible assets	123,000,000				0
Other assets, advances to/from subs	19,480,000,000				19,854,000,000
Other assets	473,000,000				66,000,000
Total assets	31,596,000,000				20,666,000,000
Liabilities
Deposits	20,193,000,000				20,605,000,000
Long-term debt	4,673,000,000				0
Other liabilities, due to/from subs	1,902,000,000				0
Other liabilities	1,970,000,000				61,000,000
Total liabilities	28,738,000,000				20,666,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | OneMain Financial Business
Discontinued operations
Income before taxes	177,000,000	242,000,000
Assets
Cash and deposits with banks	492,000,000
Investments	1,499,000,000
Loans, net	7,427,000,000
Allowance	688,000,000
Intangible assets	123,000,000
Other assets	355,000,000
Total assets	9,896,000,000
Liabilities
Long-term debt	4,673,000,000
Other liabilities, due to/from subs	1,902,000,000
Other liabilities	1,454,000,000
Total liabilities	8,029,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Japan Cards Business
Discontinued operations
Income before taxes	(1,000,000)	0
Assets
Cash and deposits with banks	16,000,000
Loans, net	1,308,000,000
Allowance	24,000,000
Goodwill	61,000,000
Other assets	66,000,000
Total assets	1,451,000,000
Liabilities
Other liabilities	460,000,000
Total liabilities	460,000,000
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Japan Retail Business
Discontinued operations
Income before taxes	0	2,000,000
Assets
Cash and deposits with banks	118,000,000				151,000,000
Loans, net	548,000,000				544,000,000
Allowance	1,000,000				2,000,000
Goodwill	51,000,000				51,000,000
Other assets, advances to/from subs	19,480,000,000				19,854,000,000
Other assets	52,000,000				66,000,000
Total assets	20,249,000,000				20,666,000,000
Liabilities
Deposits	20,193,000,000				20,605,000,000
Other liabilities	56,000,000				61,000,000
Total liabilities	20,249,000,000				20,666,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Spain Consumer Business
Discontinued operations
Income before taxes	0	21,000,000
Assets
Loans, net			1,700,000,000
Liabilities
Deposits			2,200,000,000
Additional Disclosures
Assets under management			3,400,000,000
Number of branches			45
Number of ATMs			48
Number of employees			938
Pre-tax gain on sale			243,000,000
After tax gain on sale of discontinued operations			131,000,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Greece Consumer Business
Discontinued operations
Income before taxes	0	(15,000,000)
Assets
Loans, net				353,000,000
Liabilities
Deposits				1,200,000,000
Additional Disclosures
Assets under management				1,100,000,000
Number of branches				20
Number of ATMs				85
Number of employees				719
Pre-tax gain on sale				209,000,000
After tax gain on sale of discontinued operations				$ 91,000,000