FEDERAL FUNDS, SECURITIES BORROWED, LOANED AND SUBJECT TO REPURCHASE AGREEMENTS - Offsetting (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Securities purchased under agreements to resell
Gross amounts of recognized assets	$ 223,470	$ 204,460
Gross amounts offset on the Consolidated Balance Sheet	80,843	73,476
Net amounts of assets included on the Consolidated Balance Sheet	142,627	130,984
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	111,150	103,022
Net amounts	31,477	27,962
Deposits paid for securities borrowed
Gross amounts of recognized assets	122,899	101,494
Net amounts of assets included on the Consolidated Balance Sheet	122,899	101,494
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	26,497	22,271
Net amounts	96,402	79,223
Total
Gross amounts of recognized assets	346,369	305,954
Gross amounts offset on the Consolidated Balance Sheet	80,843	73,476
Net amounts of assets included on the Consolidated Balance Sheet	265,526	232,478
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	137,647	125,293
Net amounts	127,879	107,185
Securities sold under agreements to repurchase
Gross amounts of recognized liabilities	243,398	216,122
Gross amounts offset on the Consolidated Balance Sheet	80,843	73,476
Net amounts of liabilities included on the Consolidated Balance Sheet	162,555	142,646
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	89,609	73,716
Net amounts	72,946	68,930
Deposits received for securities loaned
Gross amounts of recognized liabilities	15,155	13,305
Net amounts of liabilities included on the Consolidated Balance Sheet	15,155	13,305
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	4,341	4,079
Net amounts	10,814	9,226
Total
Gross amounts of recognized liabilities	258,553	229,427
Gross amounts offset on the Consolidated Balance Sheet	80,843	73,476
Net amounts of liabilities included on the Consolidated Balance Sheet	177,710	155,951
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	93,950	77,795
Net amounts	$ 83,760	$ 78,156