Fee-Based Revenue from Contracts with Customers - Corporate & Institutional Banking Noninterest Income Disaggregation (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Noninterest income	$ 1,872	$ 1,825
Corporate & Institutional Banking
Disaggregation of Revenue [Line Items]
Noninterest income	807	694
Corporate & Institutional Banking | In-Scope
Disaggregation of Revenue [Line Items]
Noninterest income	487	437
Corporate & Institutional Banking | Out-of-Scope
Disaggregation of Revenue [Line Items]
Noninterest income	320	257
Corporate & Institutional Banking | Treasury management fees | In-Scope
Disaggregation of Revenue [Line Items]
Noninterest income	235	216
Corporate & Institutional Banking | Capital markets fees | In-Scope
Disaggregation of Revenue [Line Items]
Noninterest income	192	175
Corporate & Institutional Banking | Commercial mortgage banking activities | In-Scope
Disaggregation of Revenue [Line Items]
Noninterest income	31	26
Corporate & Institutional Banking | Other | In-Scope
Disaggregation of Revenue [Line Items]
Noninterest income	$ 29	$ 20