Investment Securities - Schedule of Contractual Maturities of Debt Securities (Details) $ in Millions	Jun. 30, 2021 USD ($)
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	$ 7,869
Available for sale, under 1 year, fair value	7,895
Available for sale, 1 to 5 years, amortized cost	32,520
Available for sale, 1 to 5 years, fair value	32,717
Available for sale, 6 to 10 years, amortized cost	12,930
Available for sale, 6 to 10 years, fair value	13,018
Available for sale, over 10 years, amortized cost	13,689
Available for sale, over 10 years, fair value	13,867
Available for sale, amortized cost	67,008
Available for sale, fair value	67,497
US Treasury and federal agencies, direct obligations
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	1,887
Available for sale, under 1 year, fair value	1,892
Available for sale, 1 to 5 years, amortized cost	9,706
Available for sale, 1 to 5 years, fair value	9,691
Available for sale, 6 to 10 years, amortized cost	1,300
Available for sale, 6 to 10 years, fair value	1,321
Available for sale, over 10 years, amortized cost	0
Available for sale, over 10 years, fair value	0
Available for sale, amortized cost	12,893
Available for sale, fair value	12,904
Held to maturity, under 1 year, amortized cost	4,274
Held to maturity, under 1 year, fair value	4,304
Held to maturity, 1 to 5 years, amortized cost	404
Held to maturity, 1 to 5 years, fair value	411
Held to maturity, 6 to 10 years, amortized cost	0
Held to maturity, 6 to 10 years, fair value	1
Held to maturity, over 10 years, amortized cost	18
Held to maturity, over 10 years, fair value	18
Held to maturity, amortized cost	4,696
Held to maturity, fair value	4,734
US Treasury and federal agencies, mortgage-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	97
Available for sale, under 1 year, fair value	103
Available for sale, 1 to 5 years, amortized cost	909
Available for sale, 1 to 5 years, fair value	918
Available for sale, 6 to 10 years, amortized cost	5,240
Available for sale, 6 to 10 years, fair value	5,258
Available for sale, over 10 years, amortized cost	9,773
Available for sale, over 10 years, fair value	9,934
Available for sale, amortized cost	16,019
Available for sale, fair value	16,213
Held to maturity, under 1 year, amortized cost	201
Held to maturity, under 1 year, fair value	207
Held to maturity, 1 to 5 years, amortized cost	307
Held to maturity, 1 to 5 years, fair value	313
Held to maturity, 6 to 10 years, amortized cost	4,645
Held to maturity, 6 to 10 years, fair value	4,672
Held to maturity, over 10 years, amortized cost	28,255
Held to maturity, over 10 years, fair value	28,542
Held to maturity, amortized cost	33,408
Held to maturity, fair value	33,734
Total U.S. Treasury and federal agencies
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	1,984
Available for sale, under 1 year, fair value	1,995
Available for sale, 1 to 5 years, amortized cost	10,615
Available for sale, 1 to 5 years, fair value	10,609
Available for sale, 6 to 10 years, amortized cost	6,540
Available for sale, 6 to 10 years, fair value	6,579
Available for sale, over 10 years, amortized cost	9,773
Available for sale, over 10 years, fair value	9,934
Available for sale, amortized cost	28,912
Available for sale, fair value	29,117
Held to maturity, under 1 year, amortized cost	4,475
Held to maturity, under 1 year, fair value	4,511
Held to maturity, 1 to 5 years, amortized cost	711
Held to maturity, 1 to 5 years, fair value	724
Held to maturity, 6 to 10 years, amortized cost	4,645
Held to maturity, 6 to 10 years, fair value	4,673
Held to maturity, over 10 years, amortized cost	28,273
Held to maturity, over 10 years, fair value	28,560
Held to maturity, amortized cost	38,104
Held to maturity, fair value	38,468
Non-U.S. debt securities, mortgage-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	246
Available for sale, under 1 year, fair value	247
Available for sale, 1 to 5 years, amortized cost	573
Available for sale, 1 to 5 years, fair value	576
Available for sale, 6 to 10 years, amortized cost	63
Available for sale, 6 to 10 years, fair value	63
Available for sale, over 10 years, amortized cost	1,107
Available for sale, over 10 years, fair value	1,116
Available for sale, amortized cost	1,989
Available for sale, fair value	2,002
Held to maturity, under 1 year, amortized cost	40
Held to maturity, under 1 year, fair value	39
Held to maturity, 1 to 5 years, amortized cost	20
Held to maturity, 1 to 5 years, fair value	20
Held to maturity, 6 to 10 years, amortized cost	0
Held to maturity, 6 to 10 years, fair value	0
Held to maturity, over 10 years, amortized cost	173
Held to maturity, over 10 years, fair value	241
Held to maturity, amortized cost	233
Held to maturity, fair value	300
Non-U.S. debt securities, asset-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	311
Available for sale, under 1 year, fair value	310
Available for sale, 1 to 5 years, amortized cost	1,214
Available for sale, 1 to 5 years, fair value	1,214
Available for sale, 6 to 10 years, amortized cost	519
Available for sale, 6 to 10 years, fair value	520
Available for sale, over 10 years, amortized cost	407
Available for sale, over 10 years, fair value	407
Available for sale, amortized cost	2,451
Available for sale, fair value	2,451
Foreign sovereign, supranational and non-U.S. agency
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	3,448
Available for sale, under 1 year, fair value	3,453
Available for sale, 1 to 5 years, amortized cost	14,318
Available for sale, 1 to 5 years, fair value	14,438
Available for sale, 6 to 10 years, amortized cost	2,774
Available for sale, 6 to 10 years, fair value	2,779
Available for sale, over 10 years, amortized cost	21
Available for sale, over 10 years, fair value	20
Available for sale, amortized cost	20,561
Available for sale, fair value	20,690
Held to maturity, under 1 year, amortized cost	345
Held to maturity, under 1 year, fair value	345
Held to maturity, 1 to 5 years, amortized cost	1,249
Held to maturity, 1 to 5 years, fair value	1,248
Held to maturity, 6 to 10 years, amortized cost	1
Held to maturity, 6 to 10 years, fair value	1
Held to maturity, over 10 years, amortized cost	0
Held to maturity, over 10 years, fair value	0
Held to maturity, amortized cost	1,595
Held to maturity, fair value	1,594
Non-U.S. debt securities, other
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	898
Available for sale, under 1 year, fair value	900
Available for sale, 1 to 5 years, amortized cost	1,871
Available for sale, 1 to 5 years, fair value	1,894
Available for sale, 6 to 10 years, amortized cost	560
Available for sale, 6 to 10 years, fair value	555
Available for sale, over 10 years, amortized cost	85
Available for sale, over 10 years, fair value	83
Available for sale, amortized cost	3,414
Available for sale, fair value	3,432
Total non-U.S. debt securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	4,903
Available for sale, under 1 year, fair value	4,910
Available for sale, 1 to 5 years, amortized cost	17,976
Available for sale, 1 to 5 years, fair value	18,122
Available for sale, 6 to 10 years, amortized cost	3,916
Available for sale, 6 to 10 years, fair value	3,917
Available for sale, over 10 years, amortized cost	1,620
Available for sale, over 10 years, fair value	1,626
Available for sale, amortized cost	28,415
Available for sale, fair value	28,575
Held to maturity, under 1 year, amortized cost	385
Held to maturity, under 1 year, fair value	384
Held to maturity, 1 to 5 years, amortized cost	1,269
Held to maturity, 1 to 5 years, fair value	1,268
Held to maturity, 6 to 10 years, amortized cost	1
Held to maturity, 6 to 10 years, fair value	1
Held to maturity, over 10 years, amortized cost	173
Held to maturity, over 10 years, fair value	241
Held to maturity, amortized cost	1,828
Held to maturity, fair value	1,894
Asset-backed securities, student loans
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	105
Available for sale, under 1 year, fair value	107
Available for sale, 1 to 5 years, amortized cost	46
Available for sale, 1 to 5 years, fair value	46
Available for sale, 6 to 10 years, amortized cost	0
Available for sale, 6 to 10 years, fair value	0
Available for sale, over 10 years, amortized cost	102
Available for sale, over 10 years, fair value	105
Available for sale, amortized cost	253
Available for sale, fair value	258
Held to maturity, under 1 year, amortized cost	361
Held to maturity, under 1 year, fair value	355
Held to maturity, 1 to 5 years, amortized cost	109
Held to maturity, 1 to 5 years, fair value	108
Held to maturity, 6 to 10 years, amortized cost	1,102
Held to maturity, 6 to 10 years, fair value	1,115
Held to maturity, over 10 years, amortized cost	3,288
Held to maturity, over 10 years, fair value	3,323
Held to maturity, amortized cost	4,860
Held to maturity, fair value	4,901
Asset-backed securities, collateralized loan obligations
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	64
Available for sale, under 1 year, fair value	64
Available for sale, 1 to 5 years, amortized cost	825
Available for sale, 1 to 5 years, fair value	826
Available for sale, 6 to 10 years, amortized cost	1,819
Available for sale, 6 to 10 years, fair value	1,820
Available for sale, over 10 years, amortized cost	1,982
Available for sale, over 10 years, fair value	1,984
Available for sale, amortized cost	4,690
Available for sale, fair value	4,694
Non-agency CMBS and RMBS
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	0
Available for sale, under 1 year, fair value	0
Available for sale, 1 to 5 years, amortized cost	0
Available for sale, 1 to 5 years, fair value	0
Available for sale, 6 to 10 years, amortized cost	0
Available for sale, 6 to 10 years, fair value	0
Available for sale, over 10 years, amortized cost	64
Available for sale, over 10 years, fair value	65
Available for sale, amortized cost	64
Available for sale, fair value	65
Held to maturity, under 1 year, amortized cost	130
Held to maturity, under 1 year, fair value	144
Held to maturity, 1 to 5 years, amortized cost	163
Held to maturity, 1 to 5 years, fair value	163
Held to maturity, 6 to 10 years, amortized cost	2
Held to maturity, 6 to 10 years, fair value	2
Held to maturity, over 10 years, amortized cost	97
Held to maturity, over 10 years, fair value	113
Held to maturity, amortized cost	392
Held to maturity, fair value	422
Asset-backed securities, other
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	0
Available for sale, under 1 year, fair value	0
Available for sale, 1 to 5 years, amortized cost	0
Available for sale, 1 to 5 years, fair value	0
Available for sale, 6 to 10 years, amortized cost	90
Available for sale, 6 to 10 years, fair value	92
Available for sale, over 10 years, amortized cost	0
Available for sale, over 10 years, fair value	0
Available for sale, amortized cost	90
Available for sale, fair value	92
Total asset-backed securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	169
Available for sale, under 1 year, fair value	171
Available for sale, 1 to 5 years, amortized cost	871
Available for sale, 1 to 5 years, fair value	872
Available for sale, 6 to 10 years, amortized cost	1,909
Available for sale, 6 to 10 years, fair value	1,912
Available for sale, over 10 years, amortized cost	2,148
Available for sale, over 10 years, fair value	2,154
Available for sale, amortized cost	5,097
Available for sale, fair value	5,109
Held to maturity, under 1 year, amortized cost	491
Held to maturity, under 1 year, fair value	499
Held to maturity, 1 to 5 years, amortized cost	272
Held to maturity, 1 to 5 years, fair value	271
Held to maturity, 6 to 10 years, amortized cost	1,104
Held to maturity, 6 to 10 years, fair value	1,117
Held to maturity, over 10 years, amortized cost	3,385
Held to maturity, over 10 years, fair value	3,436
Held to maturity, amortized cost	5,252
Held to maturity, fair value	5,323
State and political subdivisions
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	144
Available for sale, under 1 year, fair value	144
Available for sale, 1 to 5 years, amortized cost	633
Available for sale, 1 to 5 years, fair value	655
Available for sale, 6 to 10 years, amortized cost	498
Available for sale, 6 to 10 years, fair value	539
Available for sale, over 10 years, amortized cost	148
Available for sale, over 10 years, fair value	153
Available for sale, amortized cost	1,423
Available for sale, fair value	1,491
Other U.S. debt securities
Contractual Maturities Of Debt Investment Securities [Line Items]
Available for sale, under 1 year, amortized cost	669
Available for sale, under 1 year, fair value	675
Available for sale, 1 to 5 years, amortized cost	2,425
Available for sale, 1 to 5 years, fair value	2,459
Available for sale, 6 to 10 years, amortized cost	67
Available for sale, 6 to 10 years, fair value	71
Available for sale, over 10 years, amortized cost	0
Available for sale, over 10 years, fair value	0
Available for sale, amortized cost	3,161
Available for sale, fair value	3,205
Total
Contractual Maturities Of Debt Investment Securities [Line Items]
Held to maturity, under 1 year, amortized cost	5,351
Held to maturity, under 1 year, fair value	5,394
Held to maturity, 1 to 5 years, amortized cost	2,252
Held to maturity, 1 to 5 years, fair value	2,263
Held to maturity, 6 to 10 years, amortized cost	5,750
Held to maturity, 6 to 10 years, fair value	5,791
Held to maturity, over 10 years, amortized cost	31,831
Held to maturity, over 10 years, fair value	32,237
Held to maturity, amortized cost	45,184
Held to maturity, fair value	$ 45,685