SECURITIES BORROWED, LOANED AND SUBJECT TO REPURCHASE AGREEMENTS - Repurchase Agreements (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	$ 310,509	$ 338,564
Deposits received for securities loaned	36,831	24,689
Total	347,340	363,253
U.S. Treasury and federal agency securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	108,346	112,437
Deposits received for securities loaned	2	0
Total	108,348	112,437
State and municipal securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	996	664
Deposits received for securities loaned	0	2
Total	996	666
Foreign government securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	134,204	130,017
Deposits received for securities loaned	200	194
Total	134,404	130,211
Corporate bonds
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	22,914	20,149
Deposits received for securities loaned	297	78
Total	23,211	20,227
Equity securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	22,025	21,497
Deposits received for securities loaned	36,202	24,149
Total	58,227	45,646
Mortgage-backed securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	16,576	45,566
Deposits received for securities loaned	0	0
Total	16,576	45,566
Asset-backed securities
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	1,571	3,307
Deposits received for securities loaned	0	0
Total	1,571	3,307
Other
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	3,877	4,927
Deposits received for securities loaned	130	266
Total	4,007	5,193
Open and overnight
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	137,111	160,754
Deposits received for securities loaned	26,931	17,038
Total	164,042	177,792
Up to 30 days
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	87,435	98,226
Deposits received for securities loaned	42	3
Total	87,477	98,229
31–90 days
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	33,974	41,679
Deposits received for securities loaned	2,088	2,770
Total	36,062	44,449
Greater than 90 days
Assets Sold under Agreements to Repurchase
Securities sold under agreements to repurchase	51,989	37,905
Deposits received for securities loaned	7,770	4,878
Total	$ 59,759	$ 42,783