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Capital Stock - Additional Information (Detail) - USD ($)
$ / shares in Units, shares in Millions
 3 Months Ended 12 Months Ended
Jul. 29, 2015
Mar. 31, 2017
Dec. 31, 2016
Dec. 31, 2013
Class of Stock [Line Items]        
Cost of shares repurchased   $ 473,000,000 $ 2,601,000,000  
Common Class A        
Class of Stock [Line Items]        
Number of shares repurchased   10.8    
Average cost of shares repurchased   $ 43.87    
Cost of shares repurchased   $ 500,000,000    
Stock repurchase remaining amount   2,400,000,000    
Common Class A | Share Repurchase Program amended July 29, 2015        
Class of Stock [Line Items]        
Stock repurchase value $ 13,700,000,000      
Increase in share repurchase value $ 6,000,000,000      
Stock repurchase expiration date Dec. 31, 2018      
Common Class A | Prior to January 1, 2016        
Class of Stock [Line Items]        
Stock repurchase value   $ 10,800,000,000   $ 7,700,000,000