DERIVATIVES - Derivative Notionals (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Hedging instruments under ASC 815
Derivatives
Derivative notionals	$ 438,164	$ 420,823
Hedging instruments under ASC 815 | Interest rate contracts
Derivatives
Derivative notionals	334,351	318,089
Hedging instruments under ASC 815 | Interest rate swaps
Derivatives
Derivative notionals	334,351	318,089
Hedging instruments under ASC 815 | Interest rate futures and forwards
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Interest rate contract options | Written or Sold
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Interest rate contract options | Purchased
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Foreign exchange contracts
Derivatives
Derivative notionals	102,889	101,539
Hedging instruments under ASC 815 | Foreign exchange swaps
Derivatives
Derivative notionals	65,709	63,104
Hedging instruments under ASC 815 | Foreign exchange futures, forwards and spot
Derivatives
Derivative notionals	37,080	38,275
Hedging instruments under ASC 815 | Foreign exchange contract options | Written or Sold
Derivatives
Derivative notionals	47	80
Hedging instruments under ASC 815 | Foreign exchange contract options | Purchased
Derivatives
Derivative notionals	53	80
Hedging instruments under ASC 815 | Equity contracts
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Equity swaps
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Equity futures and forwards
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Equity contract options | Written or Sold
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Equity contract options | Purchased
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Commodity and other contracts
Derivatives
Derivative notionals	924	1,195
Hedging instruments under ASC 815 | Commodity and other swaps
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Commodity and other futures and forwards
Derivatives
Derivative notionals	924	1,195
Hedging instruments under ASC 815 | Commodity and other contract options | Written or Sold
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Commodity and other contract options | Purchased
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Credit derivatives
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Credit derivatives | Written or Sold
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Credit derivatives | Purchased
Derivatives
Derivative notionals	0	0
Other derivative instruments, Trading derivatives
Derivatives
Derivative notionals	39,808,290	39,522,192
Other derivative instruments, Trading derivatives | Interest rate contracts
Derivatives
Derivative notionals	24,858,399	24,672,211
Other derivative instruments, Trading derivatives | Interest rate swaps
Derivatives
Derivative notionals	17,724,147	17,063,272
Other derivative instruments, Trading derivatives | Interest rate futures and forwards
Derivatives
Derivative notionals	4,142,514	3,636,658
Other derivative instruments, Trading derivatives | Interest rate contract options | Written or Sold
Derivatives
Derivative notionals	1,573,483	2,114,511
Other derivative instruments, Trading derivatives | Interest rate contract options | Purchased
Derivatives
Derivative notionals	1,418,255	1,857,770
Other derivative instruments, Trading derivatives | Foreign exchange contracts
Derivatives
Derivative notionals	12,320,659	11,910,251
Other derivative instruments, Trading derivatives | Foreign exchange swaps
Derivatives
Derivative notionals	6,567,304	6,063,853
Other derivative instruments, Trading derivatives | Foreign exchange futures, forwards and spot
Derivatives
Derivative notionals	3,945,391	3,979,188
Other derivative instruments, Trading derivatives | Foreign exchange contract options | Written or Sold
Derivatives
Derivative notionals	907,338	908,061
Other derivative instruments, Trading derivatives | Foreign exchange contract options | Purchased
Derivatives
Derivative notionals	900,626	959,149
Other derivative instruments, Trading derivatives | Equity contracts
Derivatives
Derivative notionals	1,110,328	1,247,562
Other derivative instruments, Trading derivatives | Equity swaps
Derivatives
Derivative notionals	274,098	197,893
Other derivative instruments, Trading derivatives | Equity futures and forwards
Derivatives
Derivative notionals	67,025	66,705
Other derivative instruments, Trading derivatives | Equity contract options | Written or Sold
Derivatives
Derivative notionals	441,003	560,571
Other derivative instruments, Trading derivatives | Equity contract options | Purchased
Derivatives
Derivative notionals	328,202	422,393
Other derivative instruments, Trading derivatives | Commodity and other contracts
Derivatives
Derivative notionals	362,527	384,855
Other derivative instruments, Trading derivatives | Commodity and other swaps
Derivatives
Derivative notionals	80,127	69,445
Other derivative instruments, Trading derivatives | Commodity and other futures and forwards
Derivatives
Derivative notionals	143,175	137,192
Other derivative instruments, Trading derivatives | Commodity and other contract options | Written or Sold
Derivatives
Derivative notionals	71,376	91,587
Other derivative instruments, Trading derivatives | Commodity and other contract options | Purchased
Derivatives
Derivative notionals	67,849	86,631
Other derivative instruments, Trading derivatives | Credit derivatives
Derivatives
Derivative notionals	1,156,377	1,307,313
Other derivative instruments, Trading derivatives | Credit derivatives | Written or Sold
Derivatives
Derivative notionals	543,607	603,387
Other derivative instruments, Trading derivatives | Credit derivatives | Purchased
Derivatives
Derivative notionals	612,770	703,926
Rule Changes Adopted by Clearing Organizations
Derivatives
Reduction in derivative assets	280,000	180,000
Reduction in derivative liabilities	$ 280,000	$ 180,000