v3.19.3.a.u2
Borrowings (Schedule of Long-Term Borrowings) (Details) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Debt Instrument [Line Items]    
Long-term borrowings $ 7,879 $ 12,424
Parent Company [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 2,950 3,102
Parent Company [Member] | Senior Notes [Member] | Three Point Two Zero Percent Senior Notes Due February 2021 [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 358 1,101
Parent Company [Member] | Senior Notes [Member] | Two Point Seven Five Percent Senior Notes Due August 2022 [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 997 996
Parent Company [Member] | Senior Notes [Member] | Three Point Eight Zero Percent Senior Notes Due August 2023 [Member] [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 996 497
Parent Company [Member] | Subordinated Debt [Member] | Seven Point Seven Five Percent Subordinated Notes Due September Two Thousand Twenty Four [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 100 100
Parent Company [Member] | Subordinated Debt [Member] | Six Point Seven Five Percent Subordinated Debentures Due November Two Thousand Twenty Five [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 156 157
Parent Company [Member] | Subordinated Debt [Member] | Seven Point Three Seven Five Percent Subordinated Notes Due December Two Thousand Thirty Seven [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 298 298
Parent Company [Member] | Valuation Adjustments On Hedged Long Term Debt [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 45 (47)
Regions Bank [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 4,929 9,322
Regions Bank [Member] | Senior Notes [Member] | Two Point Seven Five Percent Senior Notes Due April Two Thousand Twenty-One [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 549 548
Regions Bank [Member] | Senior Notes [Member] | Three Month LIBOR Plus Point Three Eight Percent of Floating Rate Senior Notes due April 2021 [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 350 349
Regions Bank [Member] | Senior Notes [Member] | Three Point Three Seven Four Percent Senior Notes Converting to Three Month LIBOR Plus Point Five Zero Percent and Callable August Two Thousand Twenty-One, Due August Two Thousand Twenty-One [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 499 499
Regions Bank [Member] | Senior Notes [Member] | Three Month LIBOR Plus Point Five Zero Percent of Floating Senior Notes, callable August 2020, due August 2021 [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 499 499
Regions Bank [Member] | Subordinated Debt [Member] | Six Point Four Five Percent Subordinated Notes Due June Two Thousand Thirty Seven [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 495 495
Regions Bank [Member] | Federal Home Loan Bank Advances [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 2,501 6,902
Regions Bank [Member] | Other Long Term Debt [Member]    
Debt Instrument [Line Items]    
Long-term borrowings 32 33
Regions Bank [Member] | Valuation Adjustments On Hedged Long Term Debt [Member]    
Debt Instrument [Line Items]    
Long-term borrowings $ 4 $ (3)