Debt - Summary of Debt Instruments (Parenthetical) (Detail)	Mar. 31, 2019	Dec. 31, 2018	Mar. 19, 2018
Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate			3.70%
4.625% [Member] | Due in 2019 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	4.625%	4.625%
2.7% [Member] | Due in 2020 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	2.70%	2.70%
3.375% [Member] | Due in 2021 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	3.375%	3.375%
3.150% [Member] | Due in 2022 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	3.15%	3.15%
3.7% [Member] | Due in 2023 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	3.70%	3.70%
3.550% [Member] | Due in 2025 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	3.55%	3.55%
4.250% [Member] | Due in 2035 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	4.25%	4.25%
5.750% [Member] | Due in 2039 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	5.75%	5.75%
4.450% [Member] | Due in 2045 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest rate	4.45%	4.45%
1.414% [Member] | Due in 2022 [Member] | Euro Notes [Member]
Debt Instrument [Line Items]
Interest rate	1.414%	1.414%
2.425% [Member] | Due in 2026 [Member] | Euro Notes [Member]
Debt Instrument [Line Items]
Interest rate	2.425%	2.425%