Investment Securities - Schedule of Gross Pre-Tax Unrealized Losses on Investment Securities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	$ 12,428	$ 17,740
Available for sale, gross unrealized losses less than 12 months	50	110
Available for sale, fair value 12 months or longer	2,626	6,886
Available for sale, gross unrealized losses 12 months or longer	24	208
Available for sale, fair value total	15,054	24,626
Available for sale, gross unrealized losses total	74	318
Held to maturity, fair value less than 12 months	8,676	9,461
Held-to-maturity, gross unrealized losses, less than 12 months	53	155
Held to maturity, fair value 12 months or longer	4,894	23,757
Held to maturity, gross unrealized losses 12 months or longer	42	583
Held to maturity, fair value total	13,570	33,218
Held to maturity, gross unrealized losses total	95	738
US Treasury and federal agencies, direct obligations
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	1,430
Available for sale, gross unrealized losses less than 12 months	28
Available for sale, fair value 12 months or longer	0
Available for sale, gross unrealized losses 12 months or longer	0
Available for sale, fair value total	1,430
Available for sale, gross unrealized losses total	28
Held to maturity, fair value less than 12 months	604	2,192
Held-to-maturity, gross unrealized losses, less than 12 months	0	45
Held to maturity, fair value 12 months or longer	2,262	12,403
Held to maturity, gross unrealized losses 12 months or longer	3	154
Held to maturity, fair value total	2,866	14,595
Held to maturity, gross unrealized losses total	3	199
US Treasury and federal agencies, mortgage-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	2,499	5,058
Available for sale, gross unrealized losses less than 12 months	7	21
Available for sale, fair value 12 months or longer	1,665	5,089
Available for sale, gross unrealized losses 12 months or longer	18	160
Available for sale, fair value total	4,164	10,147
Available for sale, gross unrealized losses total	25	181
Held to maturity, fair value less than 12 months	6,056	6,502
Held-to-maturity, gross unrealized losses, less than 12 months	31	103
Held to maturity, fair value 12 months or longer	1,606	10,648
Held to maturity, gross unrealized losses 12 months or longer	13	415
Held to maturity, fair value total	7,662	17,150
Held to maturity, gross unrealized losses total	44	518
Total U.S. Treasury and federal agencies
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	3,929	5,058
Available for sale, gross unrealized losses less than 12 months	35	21
Available for sale, fair value 12 months or longer	1,665	5,089
Available for sale, gross unrealized losses 12 months or longer	18	160
Available for sale, fair value total	5,594	10,147
Available for sale, gross unrealized losses total	53	181
Held to maturity, fair value less than 12 months	6,660	8,694
Held-to-maturity, gross unrealized losses, less than 12 months	31	148
Held to maturity, fair value 12 months or longer	3,868	23,051
Held to maturity, gross unrealized losses 12 months or longer	16	569
Held to maturity, fair value total	10,528	31,745
Held to maturity, gross unrealized losses total	47	717
Asset-backed securities, student loans
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	271	106
Available for sale, gross unrealized losses less than 12 months	1	0
Available for sale, fair value 12 months or longer	127	218
Available for sale, gross unrealized losses 12 months or longer	1	1
Available for sale, fair value total	398	324
Available for sale, gross unrealized losses total	2	1
Held to maturity, fair value less than 12 months	2,003	481
Held-to-maturity, gross unrealized losses, less than 12 months	22	4
Held to maturity, fair value 12 months or longer	778	536
Held to maturity, gross unrealized losses 12 months or longer	19	6
Held to maturity, fair value total	2,781	1,017
Held to maturity, gross unrealized losses total	41	10
Asset-backed securities, credit cards
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	89	90
Available for sale, gross unrealized losses less than 12 months	1	0
Available for sale, fair value 12 months or longer	0	493
Available for sale, gross unrealized losses 12 months or longer	0	26
Available for sale, fair value total	89	583
Available for sale, gross unrealized losses total	1	26
Asset-backed securities, collateralized loan obligations
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	862	548
Available for sale, gross unrealized losses less than 12 months	2	2
Available for sale, fair value 12 months or longer	278	0
Available for sale, gross unrealized losses 12 months or longer	1	0
Available for sale, fair value total	1,140	548
Available for sale, gross unrealized losses total	3	2
Asset-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	1,222	744
Available for sale, gross unrealized losses less than 12 months	4	2
Available for sale, fair value 12 months or longer	405	711
Available for sale, gross unrealized losses 12 months or longer	2	27
Available for sale, fair value total	1,627	1,455
Available for sale, gross unrealized losses total	6	29
Held to maturity, fair value less than 12 months	2,003	481
Held-to-maturity, gross unrealized losses, less than 12 months	22	4
Held to maturity, fair value 12 months or longer	778	536
Held to maturity, gross unrealized losses 12 months or longer	19	6
Held to maturity, fair value total	2,781	1,017
Held to maturity, gross unrealized losses total	41	10
Non-U.S. debt securities, mortgage-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	228	1,407
Available for sale, gross unrealized losses less than 12 months	0	4
Available for sale, fair value 12 months or longer	220	118
Available for sale, gross unrealized losses 12 months or longer	1	1
Available for sale, fair value total	448	1,525
Available for sale, gross unrealized losses total	1	5
Held to maturity, fair value less than 12 months	0	184
Held-to-maturity, gross unrealized losses, less than 12 months	0	2
Held to maturity, fair value 12 months or longer	138	119
Held to maturity, gross unrealized losses 12 months or longer	6	7
Held to maturity, fair value total	138	303
Held to maturity, gross unrealized losses total	6	9
Non-U.S. debt securities, asset-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	672	1,479
Available for sale, gross unrealized losses less than 12 months	1	6
Available for sale, fair value 12 months or longer	109	0
Available for sale, gross unrealized losses 12 months or longer	1	0
Available for sale, fair value total	781	1,479
Available for sale, gross unrealized losses total	2	6
Non-U.S. debt securities, government securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	3,246	5,478
Available for sale, gross unrealized losses less than 12 months	1	45
Available for sale, fair value 12 months or longer	0	0
Available for sale, gross unrealized losses 12 months or longer	0	0
Available for sale, fair value total	3,246	5,478
Available for sale, gross unrealized losses total	1	45
Non-U.S. debt securities, other
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	2,736	2,167
Available for sale, gross unrealized losses less than 12 months	9	12
Available for sale, fair value 12 months or longer	187	226
Available for sale, gross unrealized losses 12 months or longer	1	4
Available for sale, fair value total	2,923	2,393
Available for sale, gross unrealized losses total	10	16
Total non-U.S. debt securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	6,882	10,531
Available for sale, gross unrealized losses less than 12 months	11	67
Available for sale, fair value 12 months or longer	516	344
Available for sale, gross unrealized losses 12 months or longer	3	5
Available for sale, fair value total	7,398	10,875
Available for sale, gross unrealized losses total	14	72
Held to maturity, fair value less than 12 months	0	184
Held-to-maturity, gross unrealized losses, less than 12 months	0	2
Held to maturity, fair value 12 months or longer	138	119
Held to maturity, gross unrealized losses 12 months or longer	6	7
Held to maturity, fair value total	138	303
Held to maturity, gross unrealized losses total	6	9
State and political subdivisions
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	163	365
Available for sale, gross unrealized losses less than 12 months	0	3
Available for sale, fair value 12 months or longer	22	244
Available for sale, gross unrealized losses 12 months or longer	1	4
Available for sale, fair value total	185	609
Available for sale, gross unrealized losses total	1	7
Collateralized mortgage obligations
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	13	181
Available for sale, gross unrealized losses less than 12 months	0	3
Available for sale, fair value 12 months or longer	4	14
Available for sale, gross unrealized losses 12 months or longer	0	0
Available for sale, fair value total	17	195
Available for sale, gross unrealized losses total	0	3
Held to maturity, fair value less than 12 months	13	102
Held-to-maturity, gross unrealized losses, less than 12 months	0	1
Held to maturity, fair value 12 months or longer	110	51
Held to maturity, gross unrealized losses 12 months or longer	1	1
Held to maturity, fair value total	123	153
Held to maturity, gross unrealized losses total	1	2
Other U.S. debt securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	219	861
Available for sale, gross unrealized losses less than 12 months	0	14
Available for sale, fair value 12 months or longer	14	484
Available for sale, gross unrealized losses 12 months or longer	0	12
Available for sale, fair value total	233	1,345
Available for sale, gross unrealized losses total	$ 0	$ 26

Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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