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Business Combination (Details) - USD ($)
1 Months Ended 3 Months Ended 9 Months Ended
Jul. 31, 2018
Jul. 31, 2018
Sep. 30, 2018
Sep. 30, 2018
Mar. 31, 2018
Business Acquisition [Line Items]          
Long-term debt         $ 130,000,000.0
Silversea Cruises          
Business Acquisition [Line Items]          
Percentage of interests acquired 66.70% 66.70%      
Payments to acquire business $ 1,020,000,000        
Contingent consideration 44,000,000 $ 44,000,000      
Redeemable noncontrolling interest 537,770,000 537,770,000      
Transaction costs     $ 25,900,000 $ 30,600,000  
Silversea Cruises | Silversea Cruises          
Business Acquisition [Line Items]          
Long-term debt $ 700,000,000 $ 700,000,000      
Minimum | Silversea Cruises          
Business Acquisition [Line Items]          
Contingent consideration, shares (in shares)   0      
Maximum | Silversea Cruises          
Business Acquisition [Line Items]          
Contingent consideration, shares (in shares)   472,000      
Silversea Cruises Group          
Business Acquisition [Line Items]          
Ownership percentage by noncontrolling owners     33.30% 33.30%