Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	$ 348	$ 401	$ 724	$ 804
Noninterest income	609	688	1,217	1,364
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	114	121	231	244
Investment banking and debt placement fees
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	79	98	191	207
Services charges on deposit accounts
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	69	96	136	187
Cards and payments income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	83	83	160	161
Other noninterest income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	3	3	6	5
Noninterest income	243	257	461	505
Operating Segments | Consumer Bank
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	192	209	379	413
Operating Segments | Consumer Bank | Trust and investment services income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	100	103	200	208
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	41	59	80	114
Operating Segments | Consumer Bank | Cards and payments income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	48	44	93	86
Operating Segments | Consumer Bank | Other noninterest income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	3	3	6	5
Operating Segments | Commercial Bank
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	156	192	345	391
Operating Segments | Commercial Bank | Trust and investment services income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	14	18	31	36
Operating Segments | Commercial Bank | Investment banking and debt placement fees
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	79	98	191	207
Operating Segments | Commercial Bank | Services charges on deposit accounts
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	28	37	56	73
Operating Segments | Commercial Bank | Cards and payments income
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers	35	39	67	75
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]
Noninterest income	$ 18	$ 30	$ 32	$ 55