Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 379	$ 348	$ 776	$ 724
Total noninterest income	627	609	1,274	1,217
Contract assets	0	0	0	0
Contract liabilities	0	0	0	0
Trust and investment services income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	129	114	255	231
Investment banking and debt placement fees
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	99	79	229	191
Services charges on deposit accounts
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	66	69	129	136
Cards and payments income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	82	83	157	160
Other noninterest income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	3	3	6	6
Total noninterest income	213	243	441	461
Operating Segments | Consumer Bank
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	196	192	383	379
Operating Segments | Consumer Bank | Trust and investment services income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	111	100	221	200
Operating Segments | Consumer Bank | Investment banking and debt placement fees
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0	0
Operating Segments | Consumer Bank | Services charges on deposit accounts
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	35	41	68	80
Operating Segments | Consumer Bank | Cards and payments income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	47	48	88	93
Operating Segments | Consumer Bank | Other noninterest income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	3	3	6	6
Operating Segments | Commercial Bank
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	183	156	393	345
Operating Segments | Commercial Bank | Trust and investment services income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	18	14	34	31
Operating Segments | Commercial Bank | Investment banking and debt placement fees
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	99	79	229	191
Operating Segments | Commercial Bank | Services charges on deposit accounts
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	31	28	61	56
Operating Segments | Commercial Bank | Cards and payments income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	35	35	69	67
Operating Segments | Commercial Bank | Other noninterest income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	0	0	0	0
Other
Disaggregation of Revenue [Line Items]
Total noninterest income	$ 35	$ 18	$ 57	$ 32