Strategic Initiatives - Expected Charges (Details) - 2-year Restructuring Plan [Member] - USD ($) $ in Millions		Jun. 30, 2020	Mar. 31, 2020
Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges, pre-tax		$ 480	$ 400
Maximum [Member] | Wealth and Personal Banking [Member]
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges, pre-tax		34
Maximum [Member] | Commercial Banking [Member]
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges, pre-tax		10
Maximum [Member] | Global Banking and Markets [Member]
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges, pre-tax		140
Maximum [Member] | Corporate Center [Member]
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges, pre-tax	[1]	296
Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges, pre-tax		410	$ 350
Minimum [Member] | Wealth and Personal Banking [Member]
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges, pre-tax		32
Minimum [Member] | Commercial Banking [Member]
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges, pre-tax		8
Minimum [Member] | Global Banking and Markets [Member]
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges, pre-tax		120
Minimum [Member] | Corporate Center [Member]
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges, pre-tax	[1]	$ 250

[1] Includes restructuring charges primarily related to lease impairment and other related costs, as well as severance costs associated with certain centralized activities and functions.