FEDERAL FUNDS, SECURITIES BORROWED, LOANED, AND SUBJECT TO REPURCHASE AGREEMENTS - Repurchase Agreements (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	$ 202,436	$ 203,543
Security lending agreements	21,690	25,900
Gross amounts of recognized liabilities	224,126	$ 229,443
U.S. Treasury and federal agency securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	79,091
Security lending agreements	0
Gross amounts of recognized liabilities	79,091
State and municipal securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	568
Security lending agreements	0
Gross amounts of recognized liabilities	568
Foreign government
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	58,111
Security lending agreements	795
Gross amounts of recognized liabilities	58,906
Corporate
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	17,325
Security lending agreements	1,168
Gross amounts of recognized liabilities	18,493
Equity securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	13,930
Security lending agreements	19,547
Gross amounts of recognized liabilities	33,477
Mortgage-backed securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	21,041
Security lending agreements	0
Gross amounts of recognized liabilities	21,041
Asset-backed securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	5,099
Security lending agreements	0
Gross amounts of recognized liabilities	5,099
Other debt securities
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	7,271
Security lending agreements	180
Gross amounts of recognized liabilities	7,451
Open and Overnight
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	107,314
Security lending agreements	12,745
Gross amounts of recognized liabilities	120,059
Up to 30 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	51,753
Security lending agreements	5,439
Gross amounts of recognized liabilities	57,192
31-90 Days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	19,215
Security lending agreements	2,423
Gross amounts of recognized liabilities	21,638
Greater than 90 days
Assets Sold under Agreements to Repurchase [Line Items]
Repurchase agreements	24,154
Security lending agreements	1,083
Gross amounts of recognized liabilities	$ 25,237