Borrowed Funds (Schedule of Maturities of Long-Term Borrowings) (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Schedule of Maturities of Long-Term Debt [Line Items]
Long-term borrowings	$ 4,134	$ 5,993
Parent Company
Schedule of Maturities of Long-Term Debt [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	0
Long-term Debt, Maturities, Repayments of Principal in Year Two	0
Long-term Debt, Maturities, Repayments of Principal in Year Three	610
Long-term Debt, Maturities, Repayments of Principal in Year Four	0
Long-term Debt, Maturities, Repayments of Principal in Year Five	749
Long-term Debt, Maturities, Repayments of Principal after Year Five	1,278
Long-term borrowings	2,637	3,495
Regions Bank
Schedule of Maturities of Long-Term Debt [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	1,000
Long-term Debt, Maturities, Repayments of Principal in Year Two	0
Long-term Debt, Maturities, Repayments of Principal in Year Three	0
Long-term Debt, Maturities, Repayments of Principal in Year Four	0
Long-term Debt, Maturities, Repayments of Principal in Year Five	0
Long-term Debt, Maturities, Repayments of Principal after Year Five	497
Long-term borrowings	$ 1,497	$ 2,498

[Line Items] for Schedule of Maturities of Long-Term Debt [Table]

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