Restructuring Costs - Summary of Total Restructuring Costs (Details) - Transformation Program [Member] - USD ($) $ in Millions	6 Months Ended	12 Months Ended			42 Months Ended
	Jun. 30, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jun. 30, 2024
Restructuring Cost and Reserve [Line Items]
Total					$ 214
Real Estate Rationalization [Member]
Restructuring Cost and Reserve [Line Items]
Total	$ 21	$ 46	$ 79	$ 19	165
Technology Modernization [Member]
Restructuring Cost and Reserve [Line Items]
Total	0	22	19	5	46
Process Optimization [Member]
Restructuring Cost and Reserve [Line Items]
Total			1		1
Other [Member]
Restructuring Cost and Reserve [Line Items]
Total				2	2
Corporate, Non-Segment
Restructuring Cost and Reserve [Line Items]
Total					198
Corporate, Non-Segment \| Real Estate Rationalization [Member]
Restructuring Cost and Reserve [Line Items]
Total	21	46	79	19	165
Corporate, Non-Segment \| Technology Modernization [Member]
Restructuring Cost and Reserve [Line Items]
Total	0	15	16		31
Corporate, Non-Segment \| Other [Member]
Restructuring Cost and Reserve [Line Items]
Total				2	2
HWC [Member]
Restructuring Cost and Reserve [Line Items]
Total					3
HWC [Member] \| Technology Modernization [Member]
Restructuring Cost and Reserve [Line Items]
Total	0	2			2
HWC [Member] \| Process Optimization [Member]
Restructuring Cost and Reserve [Line Items]
Total			1		1
R&B [Member]
Restructuring Cost and Reserve [Line Items]
Total					13
R&B [Member] \| Technology Modernization [Member]
Restructuring Cost and Reserve [Line Items]
Total	$ 0	$ 5	$ 3	$ 5	$ 13