v3.19.3.a.u2
Stockholder Equity (Narrative) (Details)
$ / shares in Units, $ in Millions
 1 Months Ended 12 Months Ended
Feb. 29, 2020
$ / shares
shares
Dec. 31, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
shares
Dec. 31, 2019
USD ($)
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
shares
Dec. 31, 2017
$ / shares
Feb. 29, 2020
€ / shares
shares
Sep. 30, 2019
USD ($)
Class of Stock [Line Items]                
Common stock, authorized (in shares)   14,000,000,000 14,000,000,000 14,000,000,000 14,000,000,000      
Common stock, par value | $ / shares   $ 1.00 $ 1 $ 1.00 $ 1      
Common Stock, quarterly dividend declared per common shares (per share) | $ / shares   $ 0.52 $ 0.51 $ 2.05 $ 2.01 $ 1.97    
Preferred stock, authorized (in shares)   10,000,000   10,000,000        
Preferred stock, outstanding (in shares)   48,000 0 48,000 0      
Preferred stock, par value | $ / shares   $ 1   $ 1        
Preferred stock, value, issued | $   $ 0 $ 0 $ 0 $ 0      
Preferred stock, issued (in shares)   48,000 0 48,000 0      
Preferred stock, dividend rate       5.00%        
Preferred Stock, quarterly dividend declared | $   $ 8            
Tower Holdings [Member]                
Minority Interest [Line Items]                
Fixed Future Purchase Option Price | $       $ 6,000        
Puerto Rico and U.S. Virgin Islands Wireline and Wireless Operations [Member]                
Minority Interest [Line Items]                
Preferred interest, description       In December 2019, we issued $1,950 nonconvertible cumulative preferred interests in a subsidiary (PR Holdings) that holds notes secured by the proceeds from the agreement to sell wireless and wireline operations in Puerto Rico and the U.S. Virgin Islands.        
Preferred interest issued | $   $ 1,950   $ 1,950        
Preferred interest dividend requirements       The membership interests in PR Holdings consist of (1) common interests, which are held by consolidated subsidiaries of AT&T, and (2) preferred interests (PR preferred interests). The PR preferred interests pay an initial preferred distribution at an annual rate of 4.75%. Distributions are paid quarterly, subject to declaration, and reset every five years. Any failure to declare or pay distributions on the PR preferred interests would not impose any limitation on cash movements between affiliates, or our ability to declare a dividend on or repurchase AT&T shares.        
Preferred interest, redemption terms       The holders of the PR preferred interests have the option to require redemption upon the occurrence of certain contingent events, such as the failure of AT&T to pay the preferred distribution for two or more periods or to meet certain other requirements, including a minimum AT&T credit rating. If notice is given upon such an event, all other holders of equal or more subordinate classes of membership interests in PR Holdings are entitled to receive the same form of consideration payable to the holders of the preferred interests, resulting in a deemed liquidation for accounting purposes.        
Preferred interest, call or exercise features       We can call the PR preferred interests at the issue price beginning five years from the issuance date or upon the closing or termination of the sale of the underlying assets.        
Common Class A [Member] | Stock Repurchase Program March 2014 [Member]                
Equity, Class of Treasury Stock [Line Items]                
Stock Repurchase Program, Number of Shares Authorized to be Repurchased   300,000,000   300,000,000        
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased   300,000,000   300,000,000        
Common Class A [Member] | Stock Repurchase Program March 2013 [Member]                
Equity, Class of Treasury Stock [Line Items]                
Stock Repurchase Program, Number of Shares Authorized to be Repurchased   300,000,000   300,000,000        
Treasury Stock, Shares, Acquired       56,000,000        
Treasury Stock, Value, Acquired, Cost Method | $       $ 2,135        
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased   19,000,000   19,000,000        
Series A Preferred Stock [Member]                
Class of Stock [Line Items]                
Preferred stock, outstanding (in shares)   48,000 0 48,000 0      
Preferred stock, dividend payment terms       So long as the quarterly preferred dividends are declared and paid on a timely basis on each series of preferred shares, there are no limitations on our ability to declare a dividend on or repurchase AT&T common shares.        
Preferred stock, call or exercise features       The preferred shares are optionally redeemable by AT&T at the liquidation price on or after five years from the issuance date, or upon certain other contingent events.        
Preferred stock, liquidation preference per share | $ / shares   $ 25,000   $ 25,000        
Series A Preferred Stock [Member] | Mobility II, LLC                
Minority Interest [Line Items]                
Preferred interest distributions | $       $ 560        
Preferred interest dividend requirements       So long as the distributions are declared and paid, the terms of the Mobility preferred equity interests will not impose any limitations on cash movements between affiliates, or our ability to declare a dividend on or repurchase AT&T shares.        
Preferred interest, redemption terms       The price at which a put option or a redemption option can be exercised is the greater of (1) the market value of the interests as of the last date of the quarter preceding the date of the exercise of a put or redemption option and (2) the sum of (a) twenty-five dollars ($8,000 in the aggregate) plus (b) any accrued and unpaid distributions. The redemption price may be paid with cash, AT&T common stock, or a combination of cash and AT&T common stock, at Mobility II’s sole election. In no event shall Mobility II be required to deliver more than 250 million shares of AT&T common stock to settle put and redemption options.        
Preferred interest, call or exercise features       A holder of the Mobility preferred interests may put the interests to Mobility II on or after the earliest of certain events or September 9, 2020. Mobility II may redeem the interests upon a change in control of Mobility II or on or after September 9, 2022. When either options arise due to a passage of time, that option may be exercised only during certain periods.        
Preferred interest, securities issued (in shares)   320,000,000   320,000,000        
Series B Preferred Stock [Member]                
Class of Stock [Line Items]                
Preferred stock, dividend payment terms So long as the quarterly preferred dividends are declared and paid on a timely basis on each series of preferred shares, there are no limitations on our ability to declare a dividend on or repurchase AT&T common shares.              
Series B Preferred Stock [Member] | Subsequent Event [Member]                
Class of Stock [Line Items]                
Preferred stock, issued (in shares) 20,000           20,000  
Preferred stock, redemption terms The preferred shares are optionally redeemable by AT&T on or after five years from the issuance date, or upon certain other contingent events.              
Preferred stock, liquidation preference per share | € / shares             € 100,000  
Preferred stock, dividend rate 2.875%              
Series C Preferred Stock [Member]                
Class of Stock [Line Items]                
Preferred stock, dividend payment terms So long as the quarterly preferred dividends are declared and paid on a timely basis on each series of preferred shares, there are no limitations on our ability to declare a dividend on or repurchase AT&T common shares.              
Series C Preferred Stock [Member] | Subsequent Event [Member]                
Class of Stock [Line Items]                
Preferred stock, issued (in shares) 70,000           70,000  
Preferred stock, redemption terms The preferred shares are optionally redeemable by AT&T on or after five years from the issuance date, or upon certain other contingent events.              
Preferred stock, liquidation preference per share | $ / shares $ 25,000              
Preferred stock, dividend rate 4.75%              
Preferred Class A [Member] | Tower Holdings [Member]                
Minority Interest [Line Items]                
Preferred interest issued | $   $ 6,000   $ 6,000        
Preferred interest dividend requirements       The membership interests in Tower Holdings consist of (1) common interests, which are held by a consolidated subsidiary of AT&T, and (2) two series of preferred interests (collectively the “Tower preferred interests”). The September series (Class A-1) of the preferred interests totals $1,500 and pays an initial preferred distribution of 5.0%, and the December series (Class A-2) totals $4,500 and pays an initial preferred distribution of 4.75%. Distributions are paid quarterly, subject to declaration, and reset every five years. Any failure to declare or pay distributions on the Tower preferred interests would not impose any limitation on cash movements between affiliates, or our ability to declare a dividend on or repurchase AT&T shares.        
Preferred interest, redemption terms       The holders of the Tower preferred interests have the option to require redemption upon the occurrence of certain contingent events, such as the failure of AT&T to pay the preferred distribution for two or more periods or to meet certain other requirements, including a minimum credit rating. If notice is given upon such an event, all other holders of equal or more subordinate classes of membership interests in Tower Holdings are entitled to receive the same form of consideration payable to the holders of the preferred interests, resulting in a deemed liquidation for accounting purposes.        
Preferred interest, call or exercise features       We can call the Tower preferred interests at the issue price beginning five years from the issuance date or upon the receipt of proceeds from the sale of the underlying assets.        
Class A-1 [Member] | Tower Holdings [Member]                
Minority Interest [Line Items]                
Preferred interest issued | $               $ 1,500
Preferred interest dividend requirements       The September series (Class A-1) of the preferred interests totals $1,500 and pays an initial preferred distribution of 5.0%        
Class A-2 [Member] | Tower Holdings [Member]                
Minority Interest [Line Items]                
Preferred interest issued | $   $ 4,500   $ 4,500        
Preferred interest dividend requirements       the December series (Class A-2) totals $4,500 and pays an initial preferred distribution of 4.75%