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