Borrowings (Schedule of Maturities of Long-Term Borrowings) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Schedule of Maturities of Long-Term Debt [Line Items]
Long-term borrowings	$ 7,879	$ 12,424
Parent Company [Member]
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	358
Long-term Debt, Maturities, Repayments of Principal in Year Three	1,003
Long-term Debt, Maturities, Repayments of Principal in Year Four	1,035
Long-term Debt, Maturities, Repayments of Principal in Year Five	100
Long-term Debt, Maturities, Repayments of Principal after Year Five	454
Long-term borrowings	2,950	3,102
Regions Bank [Member]
Schedule of Maturities of Long-Term Debt [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	1,778
Long-term Debt, Maturities, Repayments of Principal in Year Two	2,653
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	498
Long-term borrowings	$ 4,929	$ 9,322

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

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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