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Net Income Per Share - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 6 Months Ended
Sep. 17, 2018
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Dec. 31, 2020
Earnings Per Share [Abstract]            
Dividends declared per share, in dollars per share   $ 0.77 $ 0.75 $ 1.54 $ 1.50  
Tangible equity units issued 16,500,000          
Tangible equity units proceeds $ 800          
Price for basic share (usd per share)       0.3134 0.3134  
Tangible Equity Units, Price for Shares Diluted $ 0.3839     0.3411 0.3839  
Difference between basic and diluted net income per share, in dollars per share   0.01 $ 0.01   $ 0.01  
Common stock, par value, in dollars per share   $ 0.125   $ 0.125   $ 0.125