Debt - Summary of Debt Instruments (Parenthetical) (Detail) - Senior Notes [Member]	Sep. 30, 2015	Dec. 31, 2014
1.450% [Member] | Due in 2017 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	1.45%
2.0% [Member] | Due in 2018 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	2.00%
4.625% [Member] | Due in 2019 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	4.625%	4.625%
2.70% [Member] | Due in 2020 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	2.70%
3.375% [Member] | Due in 2021 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	3.375%	3.375%
3.150% [Member] | Due in 2022 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	3.15%	5.75%
3.550% [Member] | Due in 2025 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	3.55%
4.250% [Member] | Due in 2035 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	4.25%
5.750% [Member] | Due in 2039 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	5.75%	5.75%
4.450% [Member] | Due in 2045 [Member]
Debt Instrument [Line Items]
Interest rate of Senior Notes	4.45%