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Savings and Multi-employer Pension Plans - Additional Information (Details)
€ in Millions, £ in Millions, $ in Millions
3 Months Ended 12 Months Ended
Jan. 01, 2019
Jun. 30, 2018
USD ($)
Jun. 30, 2018
EUR (€)
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2014
USD ($)
Nov. 07, 2018
GBP (£)
Dec. 31, 2015
USD ($)
Dec. 31, 2013
USD ($)
Pension And Other Postretirement Benefits Disclosure [Line Items]                    
Defined contribution plan, employer matching contribution, percent of employees' gross pay 1.00%     2.00%            
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount       $ 0.3 $ 0.2          
Other Defined Contribution Plan                    
Pension And Other Postretirement Benefits Disclosure [Line Items]                    
Defined contribution plan, cost       $ 0.4 $ 0.3 $ 0.2        
United Kingdom Merchant Navy Officers Pension Fund | Foreign Pension Plan                    
Pension And Other Postretirement Benefits Disclosure [Line Items]                    
Pension and other postretirement benefits cost (reversal of cost), total             $ 19.4      
Pension and other postretirement benefits invoice                   $ 2.6
Pension and other post-retirement benefit plans, total funding deficit | £               £ 9.0    
Merchant Navy Ratings Pension Fund                    
Pension And Other Postretirement Benefits Disclosure [Line Items]                    
Multiemployer plan, contributions by employer   $ 1.2 € 0.9              
Merchant Navy Ratings Pension Fund | Foreign Pension Plan                    
Pension And Other Postretirement Benefits Disclosure [Line Items]                    
Pension and other post-retirement benefit plans, total funding deficit                 $ 6.9