Quarterly report pursuant to Section 13 or 15(d)

Leases (Details)

v3.10.0.1
Leases (Details)
$ in Millions
Sep. 30, 2018
USD ($)
item
Dec. 31, 2017
USD ($)
Capital Leased Assets [Line Items]    
Total minimum lease payments $ 50  
Imputed interest included in payments 20  
Current capital lease obligations 1  
Non-current capital lease obligations $ 29 $ 0
Tug Vessels Under Contract [Member]    
Capital Leased Assets [Line Items]    
Tug vessels under capital lease | item 4  
Tug Vessels Received [Member]    
Capital Leased Assets [Line Items]    
Tug vessels under capital lease | item 2