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Fair Value Measurements - Fair Value of Financial Instruments and Other Non-Financial Assets (Footnote) (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Fair value of interest rate swap agreements $ 3,200 $ 5,700
Level 2 | BG Joint Venture | Shipbuilding supervision and crew training services    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Discount rate 8.00%  
Fair Value Asset (Liability) | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term receivable $ 174 $ 3,459