Long-Term Debt - Additional Information (Detail) - USD ($)			12 Months Ended
	Dec. 20, 2018	Dec. 05, 2016	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Required offer price to repurchase senior notes if change of control repurchase event and downgrade below investment grade credit rating occurs			101.00%
Maximum consolidated debt reduction for unrestricted cash and cash equivalents for debt covenant calculation			$ 200,000,000.0
Outstanding letters of credit			32,900,000
Minimum
Debt Instrument [Line Items]
Reduction of consolidated debt in the debt ratio calculation			$ 50,000,000.0
Including Acquisition Bridge Debt | Maximum
Debt Instrument [Line Items]
Debt covenant			3.50
Excluding Acquisition Bridge Debt | Maximum
Debt Instrument [Line Items]
Debt covenant			3.75
Revolving Facility
Debt Instrument [Line Items]
Credit facility commitment		$ 700,000,000.0	$ 697,700,000
Senior unsecured revolving facility, maturity period		5 years
Debt instrument maturity period			Dec. 05, 2024
Debt instrument extended maturity period	1 year
Outstanding letters of credit			$ 2,300,000	$ 2,300,000
Borrowings under revolving facility		$ 700,000,000.0	697,700,000
Short-term Line of Credit
Debt Instrument [Line Items]
Credit facility commitment			5,000,000.0
Borrowings under revolving facility			5,000,000.0
Outstanding borrowing under credit facility			$ 0	$ 0
4.25% Senior Notes, Due 2024
Debt Instrument [Line Items]
Interest rate on notes			4.25%
Maturity year			2024
Maturity date			Jul. 02, 2024
7% Debentures, Due 2025
Debt Instrument [Line Items]
Interest rate on notes			7.00%
Maturity year			2025
Maturity date			Dec. 01, 2025
3.450% Senior Notes, Due 2027
Debt Instrument [Line Items]
Interest rate on notes			3.45%
Maturity year			2027
Maturity date			Jun. 01, 2027
3.500% Senior Notes, Due 2027
Debt Instrument [Line Items]
Interest rate on notes			3.50%
Maturity year			2027
Maturity date			Dec. 15, 2027
6.25% Senior Notes, Due 2037
Debt Instrument [Line Items]
Interest rate on notes			6.25%
Maturity year			2037
Maturity date			May 01, 2037
4.250% Senior Notes, Due 2047
Debt Instrument [Line Items]
Interest rate on notes			4.25%
Maturity year			2047
Maturity date			Dec. 15, 2047
Floating Rate Senior Notes, Due 2020
Debt Instrument [Line Items]
Maturity year			2020
Maturity date			May 22, 2020
Trade Receivable Facility
Debt Instrument [Line Items]
Credit facility commitment			$ 400,000,000.0
Debt instrument maturity period			Sep. 23, 2020
Borrowings under revolving facility			$ 400,000,000.0
Trade Receivable Facility | London Interbank Offered Rate(LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate			0.725%