Fee-based Revenue from Contracts with Customers - Corporate & Institutional Banking Noninterest Income Disaggregation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Noninterest income	$ 6,955	$ 6,874	$ 6,469
Corporate & Institutional Banking
Disaggregation of Revenue [Line Items]
Noninterest income	3,062	2,537	2,406
Corporate & Institutional Banking | In-Scope Corporate and Institutional Banking Noninterest Income
Disaggregation of Revenue [Line Items]
Noninterest income	1,850	1,566	1,454
Corporate & Institutional Banking | Out-of-Scope Corporate and Institutional Banking Noninterest Income
Disaggregation of Revenue [Line Items]
Noninterest income	1,212	971	952
Corporate & Institutional Banking | Treasury management fees | In-Scope Corporate and Institutional Banking Noninterest Income
Disaggregation of Revenue [Line Items]
Noninterest income	897	840	776
Corporate & Institutional Banking | Capital markets fees | In-Scope Corporate and Institutional Banking Noninterest Income
Disaggregation of Revenue [Line Items]
Noninterest income	759	547	510
Corporate & Institutional Banking | Commercial mortgage banking activities | In-Scope Corporate and Institutional Banking Noninterest Income
Disaggregation of Revenue [Line Items]
Noninterest income	111	102	87
Corporate & Institutional Banking | Other | In-Scope Corporate and Institutional Banking Noninterest Income
Disaggregation of Revenue [Line Items]
Noninterest income	$ 83	$ 77	$ 81