Debt - Credit Facilities (Details) - USD ($)	Dec. 16, 2016	Dec. 31, 2017	Sep. 30, 2017	Apr. 13, 2017
Credit Facility [Line Items]
Commitment fees		$ 0	$ 0
Short-Term Credit Facilities Available to Non-U.S. Subsidiaries
Credit Facility [Line Items]
Maximum borrowing capacity		20,000,000
Borrowings outstanding under credit facilities		0	0
Amount utilized to support commitments in the form of letters of credit		2,000,000
Senior Unsecured Bridge Term Loan
Credit Facility [Line Items]
Maximum borrowing capacity	$ 4,350,000,000.00
Debt term	364 days
Revolving Credit Facility
Credit Facility [Line Items]
Maximum borrowing capacity				$ 1,500,000,000
Debt term	5 years
Borrowings outstanding under credit facilities		$ 0	$ 0