Quarterly report pursuant to Section 13 or 15(d)

Debt - (Letters of Credit & Surety Bonds) (Details)

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Debt - (Letters of Credit & Surety Bonds) (Details)
€ in Millions, $ in Millions
Mar. 31, 2018
USD ($)
Mar. 31, 2018
EUR (€)
Surety Bond    
Debt Instrument [Line Items]    
Surety bonds $ 404  
Letter of Credit    
Debt Instrument [Line Items]    
Letters of credit outstanding $ 76  
Letters of credit, effective yield (percent) 1.31% 1.31%
Letter of Credit | Ribera Salud    
Debt Instrument [Line Items]    
Borrowings outstanding $ 47 € 38