v3.20.4
Stockholders' Equity (Narrative) (Details)
$ / shares in Units, € / shares in Thousands, $ in Millions
 1 Months Ended 12 Months Ended
Nov. 06, 2020
USD ($)
Oct. 31, 2020
USD ($)
Dec. 31, 2020
USD ($)
$ / shares
shares
Sep. 30, 2020
USD ($)
period
Dec. 31, 2019
USD ($)
$ / shares
shares
Sep. 30, 2019
USD ($)
Dec. 31, 2020
USD ($)
$ / shares
shares
Dec. 31, 2019
USD ($)
period
$ / shares
shares
Dec. 31, 2018
USD ($)
$ / shares
Dec. 31, 2020
€ / shares
shares
Class of Stock [Line Items]                    
Common stock, authorized (in shares) | shares     14,000,000,000   14,000,000,000   14,000,000,000 14,000,000,000   14,000,000,000
Preferred stock, authorized (in shares) | shares     10,000,000   10,000,000   10,000,000 10,000,000   10,000,000
Common stock, par value (in dollars per share) | $ / shares     $ 1   $ 1   $ 1 $ 1    
Preferred stock, par value (in dollars per share) | $ / shares     $ 1   $ 1   $ 1 1    
Period post issuance date that preferred shares are optionally redeemable at liquidation price             5 years      
Equity, Class of Treasury Stock [Line Items]                    
Repurchase of common stock (in shares) | shares             142,000,000      
Amount repurchased             $ 5,278      
Preferred stock, quarterly dividend declared     $ 36   $ 8          
Common stock, quarterly dividend declared per common shares (in dollars per share) | $ / shares     $ 0.52   $ 0.52   $ 2.08 $ 2.05 $ 2.01  
Noncontrolling Interest [Line Items]                    
Redemption of nonconvertible cumulative preferred interests in subsidiary             $ 1,950 $ 0 $ 0  
Discontinued Operations, Disposed of by Sale | Puerto Rico And U.S. Virgin Islands Operations                    
Noncontrolling Interest [Line Items]                    
Redemption of nonconvertible cumulative preferred interests in subsidiary $ 1,950 $ 1,950                
Stock Repurchase Program, March 2013                    
Equity, Class of Treasury Stock [Line Items]                    
Shares authorized for repurchase (in shares) | shares     300,000,000       300,000,000     300,000,000
Stock Repurchase Program, March 2014                    
Equity, Class of Treasury Stock [Line Items]                    
Shares authorized for repurchase (in shares) | shares     300,000,000       300,000,000     300,000,000
Amount outstanding (in shares) | shares     178,000,000       178,000,000     178,000,000
Tower Holdings                    
Noncontrolling Interest [Line Items]                    
Preferred interest issued         $ 6,000     6,000    
Fixed future purchase option price               $ 6,000    
Distribution reset period               5 years    
Period post issuance date that preferred interests can be called at issue price               5 years    
Option to require redemption, certain contingent events, failure of subsidiary to pay preferred distributions, minimum number of periods | period               2    
Telco LLC                    
Noncontrolling Interest [Line Items]                    
Preferred interest issued       $ 2,000            
Initial preferred distribution percentage       4.25%            
Distribution reset period       7 years            
Period post issuance date that preferred interests can be called at issue price       7 years            
Option to require redemption, certain contingent events, failure of subsidiary to pay preferred distributions, minimum number of periods | period       2            
PR Holdings                    
Noncontrolling Interest [Line Items]                    
Preferred interest issued         $ 1,950     $ 1,950    
Initial preferred distribution percentage               4.75%    
Preferred Stock – Series A                    
Class of Stock [Line Items]                    
Preferred stock, outstanding (in shares) | shares     48,000   48,000   48,000 48,000   48,000
Preferred stock, liquidation preference per share (in dollars/Euros per share) | $ / shares     $ 25,000       $ 25,000      
Preferred stock, dividend rate             5.00%      
Preferred Stock – Series A | Mobility II, LLC                    
Noncontrolling Interest [Line Items]                    
Preferred interest, securities issued (in shares) | shares     320,000,000       320,000,000     320,000,000
Preferred interest distributions             $ 560      
Put or redemption option, minimum exercise price calculation, value added to accrued and unpaid distributions (in dollars per share) | $ / shares             $ 25      
Put or redemption option, minimum exercise price calculation, value added to accrued and unpaid distributions in the aggregate             $ 8,000      
Maximum shares of common stock required to deliver to settle put and redemption options (in shares) | shares             250,000,000      
Class A-1 | Tower Holdings                    
Noncontrolling Interest [Line Items]                    
Preferred interest issued           $ 1,500        
Initial preferred distribution percentage           5.00%        
Class A-2 | Tower Holdings                    
Noncontrolling Interest [Line Items]                    
Preferred interest issued         $ 4,500     $ 4,500    
Initial preferred distribution percentage         4.75%          
Preferred Stock – Series B                    
Class of Stock [Line Items]                    
Preferred stock, outstanding (in shares) | shares     20,000   0   20,000 0   20,000
Preferred stock, liquidation preference per share (in dollars/Euros per share) | € / shares                   € 100
Preferred stock, dividend rate             2.875%      
Preferred Stock – Series C                    
Class of Stock [Line Items]                    
Preferred stock, outstanding (in shares) | shares     70,000   0   70,000 0   70,000
Preferred stock, liquidation preference per share (in dollars/Euros per share) | $ / shares     $ 25,000       $ 25,000      
Preferred stock, dividend rate             4.75%