Condensed Consolidating Financial Statements - Narrative (Details) - USD ($)	Mar. 31, 2018	Sep. 22, 2016	Aug. 18, 2015	May 26, 2015
Condensed Financial Statements, Captions [Line Items]
Ownership interest of subsidiary (as a percent)	100.00%
Senior notes
Condensed Financial Statements, Captions [Line Items]
Debt issued			$ 2,000,000,000.0
Senior notes | 2.95% Senior Notes due in 2027
Condensed Financial Statements, Captions [Line Items]
Debt issued		$ 500,000,000
Stated interest rate (as a percent)	2.95%	2.95%
Senior notes | 4.0% Senior Notes due in 2025
Condensed Financial Statements, Captions [Line Items]
Debt issued				$ 700,000,000
Stated interest rate (as a percent)	4.00%			4.00%
Senior notes | 2.5% Senior Notes due in 2018
Condensed Financial Statements, Captions [Line Items]
Debt issued			$ 400,000,000
Stated interest rate (as a percent)			2.50%
Senior notes | 3.3% Senior Notes due in 2020
Condensed Financial Statements, Captions [Line Items]
Debt issued			$ 700,000,000
Stated interest rate (as a percent)			3.30%
Senior notes | 4.4% Senior Notes due in 2026
Condensed Financial Statements, Captions [Line Items]
Debt issued			$ 900,000,000
Stated interest rate (as a percent)			4.40%