Debt (Credit Facilities) (Details) - USD ($)
Mar. 31, 2017
Dec. 16, 2016
Sep. 30, 2016
Credit Facility [Line Items]      
Debt Instrument, Fee Amount $ 0   $ 0
term loan [Member]      
Credit Facility [Line Items]      
Line of credit facility, maximum borrowing capacity   $ 1,500,000,000  
Debt Instrument, Periodic Payment, Interest   2.50%  
Maximum debt to total capitalization ratio per the debt covenants 68.00%    
Line of Credit Facility, Amount Outstanding $ 0    
Debt Covenant, Future Maximum Debt To Total Capitalization Ratio 65.00%    
Revolving Credit Facility [Member]      
Credit Facility [Line Items]      
Line of credit facility, maximum borrowing capacity   $ 1,200,000,000  
Revolving Credit Facility Terminated   1,000,000,000  
Line of credit facility, future maximum borrowing capacity   1,500,000,000  
Maximum debt to total capitalization ratio per the debt covenants 68.00%    
Line of Credit Facility, Amount Outstanding $ 0   0
Debt Covenant, Future Maximum Debt To Total Capitalization Ratio 65.00%    
Revolving Credit Facility [Member]      
Credit Facility [Line Items]      
Revolving Credit Facility Terminated   200,000,000  
Line of Credit Facility, Amount Outstanding     0
Short term Credit Facility Non US Subs [Member]      
Credit Facility [Line Items]      
Line of credit facility, maximum borrowing capacity $ 36,000,000    
Amount utilized to support commitments in the form of letters of credit 3,000,000    
Line of Credit Facility, Amount Outstanding $ 0   $ 0
Bridge Loan [Member]      
Credit Facility [Line Items]      
Line of credit facility, maximum borrowing capacity   $ 4,350,000,000  
Maximum debt to total capitalization ratio per the debt covenants 68.00%    
Line of Credit Facility, Amount Outstanding $ 0    
Debt Covenant, Future Maximum Debt To Total Capitalization Ratio 65.00%    
Bridge Loan [Member] | term loan [Member]      
Credit Facility [Line Items]      
Debt Issuance Costs, Gross $ 19,000,000