Investment Securities - Schedule of Gross Pre-Tax Unrealized Losses on Investment Securities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	$ 7,490	$ 12,428
Available for sale, gross unrealized losses less than 12 months	19	50
Available for sale, fair value 12 months or longer	1,351	2,626
Available for sale, gross unrealized losses 12 months or longer	7	24
Available for sale, fair value total	8,841	15,054
Available for sale, gross unrealized losses total	26	74
Held to maturity, fair value less than 12 months		8,676
Held-to-maturity, gross unrealized losses, less than 12 months		53
Held to maturity, fair value 12 months or longer		4,894
Held to maturity, gross unrealized losses 12 months or longer		42
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		13,570
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		95
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	1,636	1,430
Available for sale, gross unrealized losses less than 12 months	1	28
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	1,636	1,430
Available for sale, gross unrealized losses total	1	28
Held to maturity, fair value less than 12 months		604
Held-to-maturity, gross unrealized losses, less than 12 months		0
Held to maturity, fair value 12 months or longer		2,262
Held to maturity, gross unrealized losses 12 months or longer		3
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		2,866
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		3
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	1,394	2,499
Available for sale, gross unrealized losses less than 12 months	7	7
Available for sale, fair value 12 months or longer	63	1,665
Available for sale, gross unrealized losses 12 months or longer	0	18
Available for sale, fair value total	1,457	4,164
Available for sale, gross unrealized losses total	7	25
Held to maturity, fair value less than 12 months		6,056
Held-to-maturity, gross unrealized losses, less than 12 months		31
Held to maturity, fair value 12 months or longer		1,606
Held to maturity, gross unrealized losses 12 months or longer		13
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		7,662
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		44
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	3,030	3,929
Available for sale, gross unrealized losses less than 12 months	8	35
Available for sale, fair value 12 months or longer	63	1,665
Available for sale, gross unrealized losses 12 months or longer	0	18
Available for sale, fair value total	3,093	5,594
Available for sale, gross unrealized losses total	8	53
Held to maturity, fair value less than 12 months		6,660
Held-to-maturity, gross unrealized losses, less than 12 months		31
Held to maturity, fair value 12 months or longer		3,868
Held to maturity, gross unrealized losses 12 months or longer		16
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		10,528
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		47
Asset-backed securities, student loans
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	31	271
Available for sale, gross unrealized losses less than 12 months	0	1
Available for sale, fair value 12 months or longer	197	127
Available for sale, gross unrealized losses 12 months or longer	1	1
Available for sale, fair value total	228	398
Available for sale, gross unrealized losses total	1	2
Held to maturity, fair value less than 12 months		2,003
Held-to-maturity, gross unrealized losses, less than 12 months		22
Held to maturity, fair value 12 months or longer		778
Held to maturity, gross unrealized losses 12 months or longer		19
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		2,781
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		41
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
Available for sale, gross unrealized losses less than 12 months		1
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		89
Available for sale, gross unrealized losses total		1
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	1,498	862
Available for sale, gross unrealized losses less than 12 months	4	2
Available for sale, fair value 12 months or longer	369	278
Available for sale, gross unrealized losses 12 months or longer	2	1
Available for sale, fair value total	1,867	1,140
Available for sale, gross unrealized losses total	6	3
Asset-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	1,529	1,222
Available for sale, gross unrealized losses less than 12 months	4	4
Available for sale, fair value 12 months or longer	566	405
Available for sale, gross unrealized losses 12 months or longer	3	2
Available for sale, fair value total	2,095	1,627
Available for sale, gross unrealized losses total	7	6
Held to maturity, fair value less than 12 months		2,003
Held-to-maturity, gross unrealized losses, less than 12 months		22
Held to maturity, fair value 12 months or longer		778
Held to maturity, gross unrealized losses 12 months or longer		19
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		2,781
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		41
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	600	228
Available for sale, gross unrealized losses less than 12 months	1	0
Available for sale, fair value 12 months or longer	120	220
Available for sale, gross unrealized losses 12 months or longer	1	1
Available for sale, fair value total	720	448
Available for sale, gross unrealized losses total	2	1
Held to maturity, fair value less than 12 months		0
Held-to-maturity, gross unrealized losses, less than 12 months		0
Held to maturity, fair value 12 months or longer		138
Held to maturity, gross unrealized losses 12 months or longer		6
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		138
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		6
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	1,015	672
Available for sale, gross unrealized losses less than 12 months	3	1
Available for sale, fair value 12 months or longer	446	109
Available for sale, gross unrealized losses 12 months or longer	1	1
Available for sale, fair value total	1,461	781
Available for sale, gross unrealized losses total	4	2
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	489	3,246
Available for sale, gross unrealized losses less than 12 months	0	1
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	489	3,246
Available for sale, gross unrealized losses total	0	1
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	715	2,736
Available for sale, gross unrealized losses less than 12 months	3	9
Available for sale, fair value 12 months or longer	80	187
Available for sale, gross unrealized losses 12 months or longer	0	1
Available for sale, fair value total	795	2,923
Available for sale, gross unrealized losses total	3	10
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	2,819	6,882
Available for sale, gross unrealized losses less than 12 months	7	11
Available for sale, fair value 12 months or longer	646	516
Available for sale, gross unrealized losses 12 months or longer	2	3
Available for sale, fair value total	3,465	7,398
Available for sale, gross unrealized losses total	9	14
Held to maturity, fair value less than 12 months		0
Held-to-maturity, gross unrealized losses, less than 12 months		0
Held to maturity, fair value 12 months or longer		138
Held to maturity, gross unrealized losses 12 months or longer		6
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		138
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		6
State and political subdivisions
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	95	163
Available for sale, gross unrealized losses less than 12 months	0	0
Available for sale, fair value 12 months or longer	76	22
Available for sale, gross unrealized losses 12 months or longer	2	1
Available for sale, fair value total	171	185
Available for sale, gross unrealized losses total	2	1
Collateralized mortgage obligations
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months		13
Available for sale, gross unrealized losses less than 12 months		0
Available for sale, fair value 12 months or longer		4
Available for sale, gross unrealized losses 12 months or longer		0
Available for sale, fair value total		17
Available for sale, gross unrealized losses total		0
Held to maturity, fair value less than 12 months		13
Held-to-maturity, gross unrealized losses, less than 12 months		0
Held to maturity, fair value 12 months or longer		110
Held to maturity, gross unrealized losses 12 months or longer		1
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		123
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		1
Other U.S. debt securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	17	219
Available for sale, gross unrealized losses less than 12 months	0	0
Available for sale, fair value 12 months or longer	0	14
Available for sale, gross unrealized losses 12 months or longer	0	0
Available for sale, fair value total	17	233
Available for sale, gross unrealized losses total	$ 0	$ 0

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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