DERIVATIVES - Derivative Notionals (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Hedging instruments under ASC 815
Derivatives
Derivative notionals	$ 404,520	$ 376,831
Hedging instruments under ASC 815 | Interest rate contracts
Derivatives
Derivative notionals	301,560	273,636
Hedging instruments under ASC 815 | Interest rate swaps
Derivatives
Derivative notionals	301,560	273,636
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	102,050	102,393
Hedging instruments under ASC 815 | Foreign exchange swaps
Derivatives
Derivative notionals	59,644	57,153
Hedging instruments under ASC 815 | Foreign exchange futures, forwards and spot
Derivatives
Derivative notionals	41,395	41,410
Hedging instruments under ASC 815 | Foreign exchange contract options | Written or Sold
Derivatives
Derivative notionals	494	1,726
Hedging instruments under ASC 815 | Foreign exchange contract options | Purchased
Derivatives
Derivative notionals	517	2,104
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	910	802
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	910	802
Hedging instruments under ASC 815 | Commodity and other contracts | Written or Sold
Derivatives
Derivative notionals	0	0
Hedging instruments under ASC 815 | Commodity and other contracts | 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	52,437,720	46,221,407
Other derivative instruments, Trading derivatives | Interest rate contracts
Derivatives
Derivative notionals	33,786,742	28,321,891
Other derivative instruments, Trading derivatives | Interest rate swaps
Derivatives
Derivative notionals	21,499,304	18,138,686
Other derivative instruments, Trading derivatives | Interest rate futures and forwards
Derivatives
Derivative notionals	6,717,597	4,632,257
Other derivative instruments, Trading derivatives | Interest rate contract options | Written or Sold
Derivatives
Derivative notionals	2,924,051	3,018,469
Other derivative instruments, Trading derivatives | Interest rate contract options | Purchased
Derivatives
Derivative notionals	2,645,790	2,532,479
Other derivative instruments, Trading derivatives | Foreign exchange contracts
Derivatives
Derivative notionals	15,681,275	14,963,895
Other derivative instruments, Trading derivatives | Foreign exchange swaps
Derivatives
Derivative notionals	6,894,570	6,738,158
Other derivative instruments, Trading derivatives | Foreign exchange futures, forwards and spot
Derivatives
Derivative notionals	5,769,581	5,115,504
Other derivative instruments, Trading derivatives | Foreign exchange contract options | Written or Sold
Derivatives
Derivative notionals	1,498,054	1,566,717
Other derivative instruments, Trading derivatives | Foreign exchange contract options | Purchased
Derivatives
Derivative notionals	1,519,070	1,543,516
Other derivative instruments, Trading derivatives | Equity contracts
Derivatives
Derivative notionals	1,146,715	1,065,326
Other derivative instruments, Trading derivatives | Equity swaps
Derivatives
Derivative notionals	237,294	217,580
Other derivative instruments, Trading derivatives | Equity futures and forwards
Derivatives
Derivative notionals	58,086	52,053
Other derivative instruments, Trading derivatives | Equity contract options | Written or Sold
Derivatives
Derivative notionals	490,146	454,675
Other derivative instruments, Trading derivatives | Equity contract options | Purchased
Derivatives
Derivative notionals	361,189	341,018
Other derivative instruments, Trading derivatives | Commodity and other contracts
Derivatives
Derivative notionals	409,126	349,707
Other derivative instruments, Trading derivatives | Commodity and other swaps
Derivatives
Derivative notionals	80,780	79,133
Other derivative instruments, Trading derivatives | Commodity and other futures and forwards
Derivatives
Derivative notionals	161,555	146,647
Other derivative instruments, Trading derivatives | Commodity and other contracts | Written or Sold
Derivatives
Derivative notionals	84,958	62,629
Other derivative instruments, Trading derivatives | Commodity and other contracts | Purchased
Derivatives
Derivative notionals	81,833	61,298
Other derivative instruments, Trading derivatives | Credit derivatives
Derivatives
Derivative notionals	1,413,862	1,520,588
Other derivative instruments, Trading derivatives | Credit derivatives | Written or Sold
Derivatives
Derivative notionals	666,733	724,939
Other derivative instruments, Trading derivatives | Credit derivatives | Purchased
Derivatives
Derivative notionals	$ 747,129	$ 795,649