Debt - Summary of Debt Instruments (Parenthetical) (Detail)	Mar. 31, 2015	Dec. 31, 2014
1.450% Senior Notes due 2017 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	1.45%
2.000% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	2.00%
4.625% Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	4.625%	4.625%
2.700% Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	2.70%
3.375% Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	3.375%	3.375%
3.150% Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	3.15%
3.550% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	3.55%
4.250% Senior Notes due 2035 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	4.25%
5.750% Senior Notes due 2039 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	5.75%	5.75%
4.450% Senior Notes due 2045 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	4.45%