Annual report pursuant to Section 13 and 15(d)

CONSOLIDATED BALANCE SHEETS (Parenthetical)

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CONSOLIDATED BALANCE SHEETS (Parenthetical) - shares
shares in Millions
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Treasury stock, shares 1 1    
Common Stock | Class A Common Stock:        
Common stock, shares issued 173 180 194 201
Common Stock | Class B Common Stock:        
Common stock, shares issued 687 689 693 705