Condensed Consolidating Financial Statements - Narrative (Details) - USD ($)	Dec. 31, 2018	Jun. 30, 2018	May 17, 2018	Sep. 22, 2016	Aug. 18, 2015	May 26, 2015
Senior Notes
Debt Instrument [Line Items]
Debt face amount					$ 2,000,000,000.0
Senior Notes | 4.5% Senior Notes, due 2048
Debt Instrument [Line Items]
Debt face amount			$ 500,000,000
Interest rate (as a percent)	4.50%
Senior Notes | 2.95% Senior Notes, due 2027
Debt Instrument [Line Items]
Debt face amount				$ 500,000,000
Interest rate (as a percent)	2.95%			2.95%
Senior Notes | 4.0% Senior Notes, due 2025
Debt Instrument [Line Items]
Debt face amount						$ 700,000,000
Interest rate (as a percent)	4.00%					4.00%
Senior Notes | 2.5% Senior Notes, due 2018
Debt Instrument [Line Items]
Debt face amount		$ 400,000,000			$ 400,000,000
Interest rate (as a percent)	2.50%				2.50%
Senior Notes | 3.3% Senior Notes, due 2020
Debt Instrument [Line Items]
Debt face amount					$ 700,000,000
Interest rate (as a percent)	3.30%				3.30%
Senior Notes | 4.4% Senior Notes, due 2026
Debt Instrument [Line Items]
Debt face amount					$ 900,000,000
Interest rate (as a percent)	4.40%				4.40%
S&P Financial Services LLC
Debt Instrument [Line Items]
Ownership interest of subsidiary (as a percent)	100.00%