Debt - Summary of Debt (Non-Printing) (Detail)	1 Months Ended	12 Months Ended
	Oct. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Nov. 30, 2019	Aug. 31, 2019	Mar. 31, 2019
Debt Instrument [Line Items]
Interest rate					3.85%
2.60% senior notes due 2019
Debt Instrument [Line Items]
Interest rate		2.60%	2.60%			2.60%
Maturity year		2019	2019
4.70% senior notes due 2020
Debt Instrument [Line Items]
Interest rate		4.70%	4.70%
Maturity year		2020	2020
3.15% senior notes due 2021
Debt Instrument [Line Items]
Interest rate		3.15%	3.15%
Maturity year		2021	2021
3.75% senior notes due 2021
Debt Instrument [Line Items]
Interest rate		3.75%	3.75%
Maturity year		2021	2021
4.00% senior notes due 2022
Debt Instrument [Line Items]
Interest rate		4.00%	4.00%
Maturity year		2022	2022
3.85% senior notes due 2023
Debt Instrument [Line Items]
Interest rate		3.85%	3.85%
Maturity year		2023	2023
5.00% senior notes due 2023
Debt Instrument [Line Items]
Interest rate		5.00%	5.00%	5.00%
Maturity year		2023	2023
4.00% senior notes due 2024
Debt Instrument [Line Items]
Interest rate		4.00%	4.00%		4.00%
Maturity year		2024	2024
3.90% senior notes due 2025
Debt Instrument [Line Items]
Interest rate		3.90%	3.90%		3.90%
Maturity year		2025	2025
4.20% senior notes due 2026
Debt Instrument [Line Items]
Interest rate	4.20%	4.20%	4.20%
Maturity year	2026	2026	2026
5.375% senior notes due 2036
Debt Instrument [Line Items]
Interest rate		5.375%	5.375%
Maturity year		2036	2036
5.50% senior notes due 2046
Debt Instrument [Line Items]
Interest rate		5.50%	5.50%
Maturity year		2046	2046