Derivative Instruments and Hedging Activities - Derivative Assets and Liabilities at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	$ 304,102	$ 294,039
Derivative assets, gross amount	2,649	2,675
Derivative liabilities, gross amount	2,934	2,932
Derivative Asset, netting adjustments	(1,050)	(1,005)
Derivative Liability, netting adjustments	(440)	(597)
Net Amounts as Recognized	1,599	1,670
Net Amounts as Recognized	2,494	2,335
Net valuation allowance on derivative assets and liabilities for non-performance risk	1	2
Derivatives designated as accounting hedges:
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	157,501	148,075
Derivative assets, gross amount	167	235
Derivative liabilities, gross amount	223	317
Derivatives designated as accounting hedges: | Interest rate contracts:
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	148,907	139,337
Derivative assets, gross amount	138	234
Derivative liabilities, gross amount	46	49
Derivatives designated as accounting hedges: | Interest rate contracts: | Fair value hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	69,607	68,987
Derivative assets, gross amount	4	18
Derivative liabilities, gross amount	26	26
Derivatives designated as accounting hedges: | Interest rate contracts: | Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	79,300	70,350
Derivative assets, gross amount	134	216
Derivative liabilities, gross amount	20	23
Derivatives designated as accounting hedges: | Foreign exchange and other contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	8,594	8,738
Derivative assets, gross amount	29	1
Derivative liabilities, gross amount	177	268
Derivatives designated as accounting hedges: | Foreign exchange and other contracts | Fair value hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	1,349	1,380
Derivative assets, gross amount	0	0
Derivative liabilities, gross amount	135	113
Derivatives designated as accounting hedges: | Foreign exchange and other contracts | Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	2,431	2,488
Derivative assets, gross amount	11	0
Derivative liabilities, gross amount	1	66
Derivatives designated as accounting hedges: | Foreign exchange and other contracts | Net investment hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	4,814	4,870
Derivative assets, gross amount	18	1
Derivative liabilities, gross amount	41	89
Derivatives not designated as accounting hedges:
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	146,601	145,964
Derivative assets, gross amount	2,482	2,440
Derivative liabilities, gross amount	2,711	2,615
Derivatives not designated as accounting hedges: | Customer accommodation:
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	141,649	142,137
Derivative assets, gross amount	2,441	2,399
Derivative liabilities, gross amount	2,674	2,576
Derivatives not designated as accounting hedges: | Interest rate contracts: | Customer accommodation:
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	101,903	103,489
Derivative assets, gross amount	1,224	1,188
Derivative liabilities, gross amount	1,474	1,382
Derivatives not designated as accounting hedges: | Interest rate contracts: | Other interest rate exposures
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	1,878	872
Derivative assets, gross amount	21	21
Derivative liabilities, gross amount	30	31
Derivatives not designated as accounting hedges: | Foreign exchange and other contracts | Customer accommodation:
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	5,108	5,153
Derivative assets, gross amount	43	50
Derivative liabilities, gross amount	28	47
Derivatives not designated as accounting hedges: | Commodity contracts | Customer accommodation:
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	34,638	33,495
Derivative assets, gross amount	1,174	1,161
Derivative liabilities, gross amount	1,172	1,147
Derivatives not designated as accounting hedges: | Other contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	3,074	2,955
Derivative assets, gross amount	20	20
Derivative liabilities, gross amount	$ 7	$ 8