Investment Securities - Components of Non-marketable and Other Equity Securities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Investments in qualified affordable housing projects, net	$ 920	$ 616
Non-marketable and other equity securities	2,485	1,802
Fair value accounting | Consolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	140	89
Fair value accounting | Unconsolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	222	185
Fair value accounting | Equity securities
Investment Holdings [Line Items]
Other equity securities in public companies (fair value accounting)	158	281
Fair value accounting | Other investments
Investment Holdings [Line Items]
Nonmarketable securities	95	61
Equity method accounting | Consolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	656	362
Equity method accounting | Unconsolidated venture capital and private equity fund investments
Investment Holdings [Line Items]
Nonmarketable securities	656	362
Equity method accounting | Debt funds
Investment Holdings [Line Items]
Nonmarketable securities	5	5
Equity method accounting | Other investments
Investment Holdings [Line Items]
Nonmarketable securities	$ 289	$ 203