Capital Stock - Additional Information (Detail) - USD ($)	12 Months Ended			159 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Oct. 27, 2006
Class of Stock [Line Items]
Aggregate common stock and preferred stock authorized	300,000,000
Common stock, authorized	250,000,000.0
Common stock, par value	$ 1
Preferred Stock, authorized	50,000,000
Preferred Stock, outstanding	0
Dividends declared per common share	$ 0.676	$ 0.588	$ 0.536
Share repurchase program					$ 1,000,000,000
Shares repurchased	1,700,000	500,000	1,000,000.0	24,500,000
Cost of shares repurchased	$ 84,200,000	$ 41,400,000	$ 56,100,000	$ 1,011,000,000.0
Common Stock [Member]
Class of Stock [Line Items]
Shares repurchased	1,900,000	800,000	1,100,000
Cost of shares repurchased	$ 1,900,000	$ 800,000	$ 1,100,000
Share Repurchase Program [Member]
Class of Stock [Line Items]
Cost of shares repurchased	$ 73,200,000	$ 28,700,000	$ 50,000,000.0
2006 Share Repurchase Program [Member]
Class of Stock [Line Items]
Shares repurchased	1,500,000
Cost of shares repurchased	$ 61,900,000
Settlement of Tax Withholding on Employee Equity Compensation [Member]
Class of Stock [Line Items]
Shares repurchased	200,000	300,000	100,000
Cost of shares repurchased	$ 11,000,000.0	$ 12,700,000	$ 6,100,000