v3.19.3.a.u2
Employee Benefit Plans (Presentation Of The Fair Value Of Regions' Qualified Defined-Benefit Pension Plans' Financial Assets) (Details) - USD ($)
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount $ 2,299,000,000 $ 2,105,000,000 $ 2,218,000,000
Collective Investment Trust Funds [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Alternative Investment 859,000,000 651,000,000  
Collective Investment Trust Funds [Member] | Fixed Income Funds [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Alternative Investment 681,000,000 405,000,000  
Collective Investment Trust Funds [Member] | Common Stock Fund [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Alternative Investment 178,000,000 246,000,000  
Collective Investment Trust Funds [Member] | International Fund [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Alternative Investment 0 0  
Hedge Funds [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Alternative Investment 0 1,000,000  
Real Estate Funds [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Alternative Investment 187,000,000 200,000,000  
Private Equity Funds [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Alternative Investment 101,000,000 99,000,000  
Estimate of Fair Value [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 1,152,000,000 1,154,000,000  
Estimate of Fair Value [Member] | Cash and Cash Equivalents [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 25,000,000 158,000,000  
Estimate of Fair Value [Member] | Fixed Income Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 424,000,000 364,000,000  
Estimate of Fair Value [Member] | Fixed Income Securities [Member] | US Treasury and Government [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 400,000,000 127,000,000  
Estimate of Fair Value [Member] | Fixed Income Securities [Member] | Federal Agency Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 24,000,000 21,000,000  
Estimate of Fair Value [Member] | Fixed Income Securities [Member] | Corporate Bond Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 216,000,000  
Estimate of Fair Value [Member] | Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 522,000,000 473,000,000  
Estimate of Fair Value [Member] | Equity Securities [Member] | Domestic [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 346,000,000 287,000,000  
Estimate of Fair Value [Member] | Equity Securities [Member] | International [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 176,000,000 186,000,000  
Estimate of Fair Value [Member] | Mutual Funds [Member] | International [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 181,000,000 159,000,000  
Estimate of Fair Value [Member] | Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 1,128,000,000 917,000,000  
Estimate of Fair Value [Member] | Level 1 [Member] | Cash and Cash Equivalents [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 25,000,000 158,000,000  
Estimate of Fair Value [Member] | Level 1 [Member] | Fixed Income Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 400,000,000 127,000,000  
Estimate of Fair Value [Member] | Level 1 [Member] | Fixed Income Securities [Member] | US Treasury and Government [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 400,000,000 127,000,000  
Estimate of Fair Value [Member] | Level 1 [Member] | Fixed Income Securities [Member] | Federal Agency Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 1 [Member] | Fixed Income Securities [Member] | Corporate Bond Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 1 [Member] | Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 522,000,000 473,000,000  
Estimate of Fair Value [Member] | Level 1 [Member] | Equity Securities [Member] | Domestic [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 346,000,000 287,000,000  
Estimate of Fair Value [Member] | Level 1 [Member] | Equity Securities [Member] | International [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 176,000,000 186,000,000  
Estimate of Fair Value [Member] | Level 1 [Member] | Mutual Funds [Member] | International [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 181,000,000 159,000,000  
Estimate of Fair Value [Member] | Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 24,000,000 237,000,000  
Estimate of Fair Value [Member] | Level 2 [Member] | Cash and Cash Equivalents [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 2 [Member] | Fixed Income Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 24,000,000 237,000,000  
Estimate of Fair Value [Member] | Level 2 [Member] | Fixed Income Securities [Member] | US Treasury and Government [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 2 [Member] | Fixed Income Securities [Member] | Federal Agency Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 24,000,000 21,000,000  
Estimate of Fair Value [Member] | Level 2 [Member] | Fixed Income Securities [Member] | Corporate Bond Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 216,000,000  
Estimate of Fair Value [Member] | Level 2 [Member] | Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 2 [Member] | Equity Securities [Member] | Domestic [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 2 [Member] | Equity Securities [Member] | International [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 2 [Member] | Mutual Funds [Member] | International [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 3 [Member] | Cash and Cash Equivalents [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 3 [Member] | Fixed Income Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 3 [Member] | Fixed Income Securities [Member] | US Treasury and Government [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 3 [Member] | Fixed Income Securities [Member] | Federal Agency Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 3 [Member] | Fixed Income Securities [Member] | Corporate Bond Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 3 [Member] | Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 3 [Member] | Equity Securities [Member] | Domestic [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 3 [Member] | Equity Securities [Member] | International [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount 0 0  
Estimate of Fair Value [Member] | Level 3 [Member] | Mutual Funds [Member] | International [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Plan Assets, Amount $ 0 $ 0