Commitments, Contingencies, Guarantees, and Others - Unfunded Lending Commitments: Contractual Amount and Carrying Value (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Loss Contingencies [Line Items]
Unfunded lending commitments, contractual amount	$ 394,310	$ 386,732
Off-balance sheet lending commitment, carrying value	147	176
Credit Card
Loss Contingencies [Line Items]
Unused commitments to extend credit, contractual amount	354,098	349,594
Other excluding credit card
Loss Contingencies [Line Items]
Unused commitments to extend credit, contractual amount	38,922	35,836
Off-balance sheet lending commitment, carrying value	120	144
Advised line of credit	2,600	1,800
Letter of credit
Loss Contingencies [Line Items]
Standby letters of credit and commercial letters of credit, contractual amount	1,290	1,302
Off-balance sheet lending commitment, carrying value	$ 27	$ 32