DISCONTINUED OPERATIONS AND SIGNIFICANT DISPOSALS - Significant Disposals (Details) $ in Millions			3 Months Ended		9 Months Ended
	Sep. 30, 2014 USD ($) employee branch atm	Sep. 22, 2014 USD ($) employee branch atm	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($) employee branch atm	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($) employee branch atm	Dec. 31, 2014 USD ($)
Disposal Group, Held-for-sale, Not Discontinued Operations
Assets
Cash and deposits with banks			$ 665		$ 665		$ 151
Investments			1,403		1,403		0
Loans, net			9,627		9,627		544
Allowance			690		690		2
Goodwill			112		112		51
Intangible assets			155		155		0
Other assets, advances to/from subs			19,036		19,036		19,854
Other assets			542		542		66
Total assets			31,540		31,540		20,666
Liabilities
Deposits			19,779		19,779		20,605
Long-term debt			6,179		6,179		0
Short-term borrowings			1,136		1,136		0
Other liabilities, due to/from subs			292		292		0
Other liabilities			1,615		1,615		61
Total liabilities			29,001		29,001		20,666
Disposal Group, Held-for-sale, Not Discontinued Operations | OneMain Financial Business
Discontinued operations
Income (loss) before taxes			216	$ 223	570	$ 710
Assets
Cash and deposits with banks			523		523
Investments			1,403		1,403
Loans, net			7,731		7,731
Allowance			666		666
Intangible assets			155		155
Other assets			417		417
Total assets			10,229		10,229
Liabilities
Long-term debt			6,179		6,179
Short-term borrowings			1,136		1,136
Other liabilities, due to/from subs			292		292
Other liabilities			1,106		1,106
Total liabilities			8,713		8,713
Disposal Group, Held-for-sale, Not Discontinued Operations | Japan Cards Business
Discontinued operations
Income (loss) before taxes			4	1	13	0
Assets
Cash and deposits with banks			16		16
Loans, net			1,332		1,332
Allowance			23		23
Goodwill			61		61
Other assets			77		77
Total assets			1,486		1,486
Liabilities
Other liabilities			463		463
Total liabilities			463		463
Disposal Group, Held-for-sale, Not Discontinued Operations | Japan Retail Business
Discontinued operations
Income (loss) before taxes			(22)	5	(2)	5
Assets
Cash and deposits with banks			126		126		151
Loans, net			564		564		544
Allowance			1		1		2
Goodwill			51		51		51
Other assets, advances to/from subs			19,036		19,036		19,854
Other assets			48		48		66
Total assets			19,825		19,825		20,666
Liabilities
Deposits			19,779		19,779		20,605
Other liabilities			46		46		61
Total liabilities			19,825		19,825		$ 20,666
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Spain Consumer Business
Discontinued operations
Income (loss) before taxes			0	340	0	373
Assets
Loans, net		$ 1,700
Liabilities
Deposits		2,200
Additional Disclosures
Assets under management		$ 3,400
Number of branches | branch		45
Number of ATMs | atm		48
Number of employees | employee		938
Pre-tax gain on sale		$ 243
After tax gain on sale of discontinued operations		$ 131
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Greece Consumer Business
Discontinued operations
Income (loss) before taxes			$ 0	173	$ 0	133
Assets
Loans, net	$ 353			353		353
Liabilities
Deposits	1,200			1,200		1,200
Additional Disclosures
Assets under management	$ 1,100			$ 1,100		$ 1,100
Number of branches | branch	20			20		20
Number of ATMs | atm	85			85		85
Number of employees | employee	719			719		719
Pre-tax gain on sale	$ 209
After tax gain on sale of discontinued operations	$ 91