Subsequent Event - Issuance and Redemption of Senior Notes (Details) - Senior notes - USD ($)	Oct. 18, 2017	Aug. 28, 2017	Oct. 04, 2017
5.00% Senior Notes October 2017 | Subsequent Event
Subsequent Event [Line Items]
Aggregate principal amount of debt issued			$ 1,500,000,000
Stated interest rate			5.00%
5.00% Senior Notes Indenture 2017
Subsequent Event [Line Items]
Aggregate principal amount of debt issued		$ 1,300,000,000
Stated interest rate		5.00%
6.00% Senior Notes Indenture 2014
Subsequent Event [Line Items]
Stated interest rate		6.00%
Debt redemption amount		$ 1,250,000,000
6.00% Senior Notes Indenture 2014 | Subsequent Event
Subsequent Event [Line Items]
Debt redemption amount	$ 1,000,000,000