Fair Value of Assets and Liabilities - Nonrecurring Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	$ 88	$ 51
Loans and leases	61,778	58,102
Non Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans and leases	223	135
OREO	4	3
Other assets	92	91
Non Recurring | Loans held for sale—SBAs and USDA
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	496	506
Non Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans and leases	0	0
OREO	0	0
Other assets	0	0
Non Recurring | Level 1 | Loans held for sale—SBAs and USDA
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	0	0
Non Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans and leases	0	0
OREO	0	0
Other assets	0	0
Non Recurring | Level 2 | Loans held for sale—SBAs and USDA
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	496	506
Non Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans and leases	223	135
OREO	4	3
Other assets	92	91
Non Recurring | Level 3 | Loans held for sale—SBAs and USDA
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale	$ 0	$ 0