FEDERAL FUNDS, SECURITIES BORROWED, LOANED AND SUBJECT TO REPURCHASE AGREEMENTS - Repurchase Agreements (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	$ 216,122	$ 170,496	$ 170,496
Deposits received for securities loaned	13,305	15,958	15,958
Total	229,427	186,454	186,454
U.S. Treasury and federal agency securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	58,774		66,263
Deposits received for securities loaned	0		0
Total	58,774		66,263
State and municipal securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	1,605		334
Deposits received for securities loaned	0		0
Total	1,605		334
Foreign government
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	89,576		52,988
Deposits received for securities loaned	105		1,390
Total	89,681		54,378
Corporate
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	20,194		17,164
Deposits received for securities loaned	657		630
Total	20,851		17,794
Equity securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	20,724		12,206
Deposits received for securities loaned	11,907		13,913
Total	32,631		26,119
Mortgage-backed securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	17,791		11,421
Deposits received for securities loaned	0		0
Total	17,791		11,421
Asset-backed securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	5,479		5,428
Deposits received for securities loaned	0		0
Total	5,479		5,428
Other debt securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	1,979		4,692
Deposits received for securities loaned	636		25
Total	2,615		$ 4,717
Open and overnight
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	82,073	79,740
Deposits received for securities loaned	9,946	10,813
Total	92,019	90,553
Up to 30 days
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	68,372	50,399
Deposits received for securities loaned	266	2,169
Total	68,638	52,568
31–90 days
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	33,846	19,396
Deposits received for securities loaned	1,912	2,044
Total	35,758	21,440
Greater than 90 days
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	31,831	20,961
Deposits received for securities loaned	1,181	932
Total	$ 33,012	$ 21,893