Debt - Summary of Debt (Detail) - USD ($)		Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	May 31, 2023	Mar. 31, 2022	Mar. 31, 2020	Oct. 31, 2018	Mar. 31, 2018	Apr. 30, 2017	Aug. 31, 2016	Jan. 31, 2015	Apr. 30, 2014	Nov. 30, 2002	Mar. 31, 1999
Debt Instrument [Line Items]
Debt	[1]	$ 6,891,800,000	$ 6,888,600,000	$ 6,887,600,000
Fair value		6,498,300,000	6,431,300,000	5,932,100,000
2.45% Senior Notes due 2027 (issued: $500.0, August 2016)
Debt Instrument [Line Items]
Long-term debt		498,900,000	498,600,000	498,500,000
Fair value		483,200,000	468,900,000	455,800,000
Debt, stated interest rate											2.45%
Debt, face amount											$ 500,000,000.0
2.50% Senior Notes due 2027 (issued: $500.0, March 2022)
Debt Instrument [Line Items]
Long-term debt		498,500,000	498,100,000	497,900,000
Fair value		482,100,000	469,100,000	454,000,000.0
Debt, stated interest rate						2.50%
Debt, face amount						$ 500,000,000.0
6 5/8% Senior Notes due 2029 (issued: $300.0, March 1999)
Debt Instrument [Line Items]
Long-term debt		298,100,000	297,800,000	297,700,000
Fair value		330,100,000	328,700,000	320,800,000
Debt, stated interest rate															6.625%
Debt, face amount															$ 300,000,000.0
4.00% Senior Notes due 2029 (issued: $550.0, October 2018)
Debt Instrument [Line Items]
Long-term debt		547,300,000	546,900,000	546,800,000
Fair value		548,600,000	542,600,000	518,900,000
Debt, stated interest rate								4.00%
Debt, face amount								$ 550,000,000.0
3.20% Senior Notes due 2030 (issued: $500.0, March 2020)
Debt Instrument [Line Items]
Long-term debt		497,600,000	497,300,000	497,200,000
Fair value		476,100,000	462,200,000	435,100,000
Debt, stated interest rate							3.20%
Debt, face amount							$ 500,000,000.0
3.00% Senior Notes due 2032 (issued: $500.0, March 2022)
Debt Instrument [Line Items]
Long-term debt		496,600,000	496,300,000	496,200,000
Fair value		458,500,000	446,000,000.0	420,500,000
Debt, stated interest rate						3.00%
Debt, face amount						$ 500,000,000.0
6.25% Senior Notes due 2032 (issued: $400.0, November 2002)
Debt Instrument [Line Items]
Long-term debt		396,900,000	396,700,000	396,600,000
Fair value		449,900,000	445,600,000	414,300,000
Debt, stated interest rate														6.25%
Debt, face amount														$ 400,000,000.0
4.95% Senior Notes due 2033 (issued: $500.0, May 2023)
Debt Instrument [Line Items]
Long-term debt		496,700,000	496,400,000	496,400,000
Fair value		518,700,000	513,000,000.0	474,700,000
Debt, stated interest rate					4.95%
Debt, face amount					$ 500,000,000.0
4.35% Senior Notes due 2044 (issued: $350.0, April 2014)
Debt Instrument [Line Items]
Long-term debt		347,000,000.0	347,000,000.0	347,000,000.0
Fair value		318,900,000	314,200,000	280,900,000
Debt, stated interest rate													4.35%
Debt, face amount													$ 350,000,000.0
3.70% Senior Notes due 2045 (issued: $400.0, January 2015)
Debt Instrument [Line Items]
Long-term debt		396,000,000.0	395,900,000	395,800,000
Fair value		330,600,000	325,100,000	288,200,000
Debt, stated interest rate												3.70%
Debt, face amount												$ 400,000,000.0
4.125% Senior Notes due 2047 (issued: $850.0, April 2017)
Debt Instrument [Line Items]
Long-term debt		842,400,000	842,300,000	842,200,000
Fair value		749,800,000	756,200,000	666,300,000
Debt, stated interest rate										4.125%
Debt, face amount										$ 850,000,000.0
4.20% Senior Notes due 2048 (issued: $600.0, March 2018)
Debt Instrument [Line Items]
Long-term debt		590,800,000	590,600,000	590,600,000
Fair value		532,300,000	534,100,000	473,300,000
Debt, stated interest rate									4.20%
Debt, face amount									$ 600,000,000.0
3.95% Senior Notes due 2050 (issued: $500.0, March 2020)
Debt Instrument [Line Items]
Long-term debt		491,300,000	491,100,000	491,100,000
Fair value		420,000,000.0	422,300,000	373,500,000
Debt, stated interest rate							3.95%
Debt, face amount							$ 500,000,000.0
3.70% Senior Notes due 2052 (issued: $500.0, March 2022)
Debt Instrument [Line Items]
Long-term debt		493,700,000	493,600,000	493,600,000
Fair value		$ 399,500,000	$ 403,300,000	$ 355,800,000
Debt, stated interest rate						3.70%
Debt, face amount						$ 500,000,000.0

[1] Consists of long-term debt. See Note 4 – Debt for further discussion.