Restructuring Costs - Summary of Total Restructuring Costs (Details) - Transformation Program [Member] - USD ($) $ in Millions	9 Months Ended	12 Months Ended			45 Months Ended
	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2024
Restructuring Cost and Reserve [Line Items]
Total					$ 222
Real Estate Rationalization [Member]
Restructuring Cost and Reserve [Line Items]
Total	$ 28	$ 46	$ 79	$ 19	172
Technology Modernization [Member]
Restructuring Cost and Reserve [Line Items]
Total	1	22	19	5	47
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					206
Corporate, Non-Segment \| Real Estate Rationalization [Member]
Restructuring Cost and Reserve [Line Items]
Total	28	46	79	19	172
Corporate, Non-Segment \| Technology Modernization [Member]
Restructuring Cost and Reserve [Line Items]
Total	1	15	16		32
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