FEDERAL FUNDS, SECURITIES BORROWED, LOANED AND SUBJECT TO REPURCHASE AGREEMENTS - Offsetting (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Securities purchased under agreements to resell
Gross amounts of recognized assets	$ 220,159	$ 204,460
Gross amounts offset on the Consolidated Balance Sheet	86,543	73,476
Net amounts of assets included on the Consolidated Balance Sheet	133,616	130,984
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	101,046	103,022
Net amounts	32,570	27,962
Deposits paid for securities borrowed
Gross amounts of recognized assets	124,271	101,494
Net amounts of assets included on the Consolidated Balance Sheet	124,271	101,494
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	24,560	22,271
Net amounts	99,711	79,223
Total
Gross amounts of recognized assets	344,430	305,954
Gross amounts offset on the Consolidated Balance Sheet	86,543	73,476
Net amounts of assets included on the Consolidated Balance Sheet	257,887	232,478
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	125,606	125,293
Net amounts	132,281	107,185
Securities sold under agreements to repurchase
Gross amounts of recognized liabilities	244,093	216,122
Gross amounts offset on the Consolidated Balance Sheet	86,543	73,476
Net amounts of liabilities included on the Consolidated Balance Sheet	157,550	142,646
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	79,626	73,716
Net amounts	77,924	68,930
Deposits received for securities loaned
Gross amounts of recognized liabilities	13,884	13,305
Net amounts of liabilities included on the Consolidated Balance Sheet	13,884	13,305
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	4,528	4,079
Net amounts	9,356	9,226
Total
Gross amounts of recognized liabilities	257,977	229,427
Gross amounts offset on the Consolidated Balance Sheet	86,543	73,476
Net amounts of liabilities included on the Consolidated Balance Sheet	171,434	155,951
Amounts not offset on the Consolidated Balance Sheet but eligible for offsetting upon counterparty default	84,154	77,795
Net amounts	$ 87,280	$ 78,156