Net Income Per Share - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Sep. 17, 2018	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Earnings Per Share [Abstract]
Dividends declared per share, in dollars per share		$ 0.77	$ 0.75
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	0.3665	0.3839
Difference between basic and diluted net income per share, in dollars per share			$ 0.01
Common stock, par value, in dollars per share		$ 0.125		$ 0.125