INCOME TAXES - Deferred Income Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets
Credit loss deduction	$ 3,423	$ 5,146
Deferred compensation and employee benefits	1,585	3,798
Repositioning and settlement reserves	454	1,033
U.S. tax on non-U.S. earnings	2,452	10,050
Investment and loan basis differences	3,384	5,594
Cash flow hedges	233	327
Tax credit and net operating loss carry-forwards	21,575	20,793
Fixed assets and leases	1,090	1,739
Other deferred tax assets	1,988	2,714
Gross deferred tax assets	36,184	51,194
Valuation allowance	9,387	0
Deferred tax assets after valuation allowance	26,797	51,194
Deferred tax liabilities
Intangibles	(1,247)	(1,711)
Debt issuances	(294)	(641)
Non-U.S. withholding taxes	(668)	(739)
Interest-related items	(562)	(765)
Other deferred tax liabilities	(1,545)	(670)
Gross deferred tax liabilities	(4,316)	(4,526)
Net deferred tax assets	$ 22,481	$ 46,668