Investment Securities - Schedule of Gross Pre-Tax Unrealized Losses on Investment Securities (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	$ 22,705	$ 7,490
Available for sale, gross unrealized losses less than 12 months	147	19
Available for sale, fair value 12 months or longer	1,056	1,351
Available for sale, gross unrealized losses 12 months or longer	5	7
Available for sale, fair value total	23,761	8,841
Available for sale, gross unrealized losses total	152	26
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	6,427	1,636
Available for sale, gross unrealized losses less than 12 months	28	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	6,427	1,636
Available for sale, gross unrealized losses total	28	1
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	4,234	1,394
Available for sale, gross unrealized losses less than 12 months	55	7
Available for sale, fair value 12 months or longer	115	63
Available for sale, gross unrealized losses 12 months or longer	2	0
Available for sale, fair value total	4,349	1,457
Available for sale, gross unrealized losses total	57	7
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	10,661	3,030
Available for sale, gross unrealized losses less than 12 months	83	8
Available for sale, fair value 12 months or longer	115	63
Available for sale, gross unrealized losses 12 months or longer	2	0
Available for sale, fair value total	10,776	3,093
Available for sale, gross unrealized losses total	85	8
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	49	600
Available for sale, gross unrealized losses less than 12 months	0	1
Available for sale, fair value 12 months or longer	37	120
Available for sale, gross unrealized losses 12 months or longer	0	1
Available for sale, fair value total	86	720
Available for sale, gross unrealized losses total	0	2
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	535	1,015
Available for sale, gross unrealized losses less than 12 months	1	3
Available for sale, fair value 12 months or longer	674	446
Available for sale, gross unrealized losses 12 months or longer	1	1
Available for sale, fair value total	1,209	1,461
Available for sale, gross unrealized losses total	2	4
Foreign sovereign, supranational and non-U.S. agency
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	7,309	489
Available for sale, gross unrealized losses less than 12 months	42	0
Available for sale, fair value 12 months or longer	2	0
Available for sale, gross unrealized losses 12 months or longer	0	0
Available for sale, fair value total	7,311	489
Available for sale, gross unrealized losses total	42	0
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	976	715
Available for sale, gross unrealized losses less than 12 months	17	3
Available for sale, fair value 12 months or longer	69	80
Available for sale, gross unrealized losses 12 months or longer	0	0
Available for sale, fair value total	1,045	795
Available for sale, gross unrealized losses total	17	3
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	8,869	2,819
Available for sale, gross unrealized losses less than 12 months	60	7
Available for sale, fair value 12 months or longer	782	646
Available for sale, gross unrealized losses 12 months or longer	1	2
Available for sale, fair value total	9,651	3,465
Available for sale, gross unrealized losses total	61	9
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
Available for sale, gross unrealized losses less than 12 months		0
Available for sale, fair value 12 months or longer		197
Available for sale, gross unrealized losses 12 months or longer		1
Available for sale, fair value total		228
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	2,535	1,498
Available for sale, gross unrealized losses less than 12 months	1	4
Available for sale, fair value 12 months or longer	113	369
Available for sale, gross unrealized losses 12 months or longer	0	2
Available for sale, fair value total	2,648	1,867
Available for sale, gross unrealized losses total	1	6
Asset-backed securities
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	2,535	1,529
Available for sale, gross unrealized losses less than 12 months	1	4
Available for sale, fair value 12 months or longer	113	566
Available for sale, gross unrealized losses 12 months or longer	0	3
Available for sale, fair value total	2,648	2,095
Available for sale, gross unrealized losses total	1	7
State and political subdivisions
Gross Pre-Tax Unrealized Losses On Investment Securities [Line Items]
Available for sale, fair value less than 12 months	126	95
Available for sale, gross unrealized losses less than 12 months	0	0
Available for sale, fair value 12 months or longer	46	76
Available for sale, gross unrealized losses 12 months or longer	2	2
Available for sale, fair value total	172	171
Available for sale, gross unrealized losses total	2	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	514	17
Available for sale, gross unrealized losses less than 12 months	3	0
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	514	17
Available for sale, gross unrealized losses total	$ 3	$ 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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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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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 less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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