v3.10.0.1
Equity - Narrative (Details)
 2 Months Ended 3 Months Ended 12 Months Ended
Feb. 12, 2019
USD ($)
shares
Feb. 07, 2019
USD ($)
Sep. 07, 2018
$ / shares
shares
Mar. 14, 2018
USD ($)
$ / shares
shares
Mar. 12, 2018
USD ($)
May 19, 2017
shares
Feb. 06, 2017
USD ($)
$ / shares
shares
Feb. 02, 2017
USD ($)
Jun. 20, 2016
$ / shares
shares
Mar. 10, 2016
USD ($)
$ / shares
shares
Mar. 08, 2016
USD ($)
Mar. 11, 2018
USD ($)
 [1]
May 19, 2017
$ / shares
Dec. 31, 2018
USD ($)
employee_stock_ownership_plan
$ / shares
shares
Dec. 31, 2017
USD ($)
shares
Dec. 31, 2016
USD ($)
shares
Feb. 28, 2019
USD ($)
Dec. 31, 2015
USD ($)
Oct. 23, 2014
USD ($)
Equity, Class of Treasury Stock [Line Items]                                      
Amount of shares authorized in stock purchase plan, value                     $ 5,000,000,000               $ 11,000,000,000
Amount of remaining shares authorized in stock purchase plan, value                           $ 14,200,000,000          
Accelerated share repurchases, cash paid                   $ (5,000,000,000)                  
Shares repurchased | shares                 18,000,000 136,000,000       307,000,000 [1] 150,000,000 [2] 154,000,000 [3]      
Shares repurchased, initial price per share (in dollars per share) | $ / shares                   $ 29.36                  
Accelerated share repurchase, percentage of agreement                     80.00%                
Accelerated share repurchase, final average price paid (in dollars per share) | $ / shares                 $ 32.38                    
Cost of purchase                       $ 8,200,000,000   $ 12,198,000,000 [1],[4] $ 5,000,000,000 [2],[4] $ 5,000,000,000 [3],[4]      
Number of employee stock ownership plans | employee_stock_ownership_plan                           2          
Common ESOP Plan [Member]                                      
Equity, Class of Treasury Stock [Line Items]                                      
ESOP compensation expense                           $ 19,000,000 11,000,000 $ 9,000,000      
Preferred Stock [Member] | Series A, Convertible Preferred Stock [Member] | Preferred Employee Stock Ownership Plan [Member]                                      
Equity, Class of Treasury Stock [Line Items]                                      
Series A convertible perpetual preferred stock, dividends rate                           6.25%          
Series A convertible perpetual preferred stock, per share stated value (in dollars per share) | $ / shares                           $ 40,300          
Preferred stock, redemption price per share (in dollars per share) | $ / shares                           $ 40,300          
Common Stock [Member] | Preferred Employee Stock Ownership Plan [Member]                                      
Equity, Class of Treasury Stock [Line Items]                                      
Series A convertible perpetual preferred stock, common stock shares when converted (in shares) | shares                           2,574.87          
Convertible preferred stock, number of shares convertible | shares                           1,000,000          
Common Stock [Member] | Common ESOP Plan [Member]                                      
Equity, Class of Treasury Stock [Line Items]                                      
Number of shares in ESOP | shares                           49,000,000          
December 2015 Stock Purchase Plan [Member]                                      
Equity, Class of Treasury Stock [Line Items]                                      
Amount of shares authorized in stock purchase plan, value                                   $ 11,000,000,000  
December 2017 Stock Purchase Plan [Member]                                      
Equity, Class of Treasury Stock [Line Items]                                      
Amount of shares authorized in stock purchase plan, value                             $ 10,000,000,000        
Amount of remaining shares authorized in stock purchase plan, value                           $ 4,200,000,000          
December 2018 Stock Purchase Plan [Member]                                      
Equity, Class of Treasury Stock [Line Items]                                      
Amount of shares authorized in stock purchase plan, value                           $ 10,000,000,000          
Share Repurchase Agreement with Citibank [Member]                                      
Equity, Class of Treasury Stock [Line Items]                                      
Amount of shares authorized in stock purchase plan, value         $ 4,000,000,000     $ 5,000,000,000                      
Accelerated share repurchases, cash paid       $ (4,000,000,000)     $ (5,000,000,000)                        
Shares repurchased | shares     21,000,000 87,000,000   24,000,000 126,000,000                        
Shares repurchased, initial price per share (in dollars per share) | $ / shares       $ 36.61     $ 31.73                        
Accelerated share repurchase, percentage of agreement         80.00%     80.00%                      
Accelerated share repurchase, final average price paid (in dollars per share) | $ / shares     $ 36.86                                
Accelerated share repurchase, average price paid per share (in dollars per share) | $ / shares                         $ 33.31            
Subsequent Event [Member]                                      
Equity, Class of Treasury Stock [Line Items]                                      
Amount of shares authorized in stock purchase plan, value   $ 6,800,000,000                                  
Amount of remaining shares authorized in stock purchase plan, value                                 $ 5,300,000,000    
Accelerated share repurchases, cash paid $ 6,800,000,000                                    
Shares repurchased | shares 130,000,000                                    
Accelerated share repurchase, percentage of agreement   80.00%                                  
[1] Represents shares purchased pursuant to the accelerated share repurchase agreement with Citibank entered into on March 12, 2018, as well as other share repurchases. See above for additional information.
[2] Represents shares purchased pursuant to the accelerated share repurchase agreement with Citibank entered into on February 2, 2017. See above for additional information.
[3] Represents shares purchased pursuant to the accelerated share repurchase agreement entered into on March 8, 2016. See above for additional information.
[4] Amounts may not add due to rounding.