Summary of Significant Accounting Policies - Long Lived Assets and Deferred Costs (Details) - USD ($)
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Property Plant And Equipment [Line Items]      
Annual growth factor management fees every second year 3.00%    
Utilization rate of fleet 99.60%    
Amortization of deferred drydock and special survey costs $ 11,714,000 $ 13,828,000 $ 14,727,000
Amortization and write-off of deferred financing 8,242,000 7,880,000 6,391,000
Continuing operations      
Property Plant And Equipment [Line Items]      
Amortization of deferred drydock and special survey costs 11,067,000 13,828,000 14,727,000
Amortization and write-off of deferred financing 7,746,000 7,866,000 6,391,000
Vessels      
Property Plant And Equipment [Line Items]      
Scrap value of vessels per LWT 340    
Capitalized interest costs 1,960,000 1,908,000 4,764,000
Two dry bulk vessels held and used      
Property Plant And Equipment [Line Items]      
Impairment loss $ 84,584,000    
Four dry bulk vessels held and used      
Property Plant And Equipment [Line Items]      
Impairment loss   $ 179,186,000  
One dry bulk vessel held and used      
Property Plant And Equipment [Line Items]      
Impairment loss     $ 32,930,000
Ocean-going vessels | Minimum      
Property Plant And Equipment [Line Items]      
Period of review of special costs of assets 30 months    
Ocean-going vessels | Maximum      
Property Plant And Equipment [Line Items]      
Period of review of special costs of assets 60 months    
Pushboats and barges | Minimum      
Property Plant And Equipment [Line Items]      
Period of review of special costs of assets 72 months    
Pushboats and barges | Maximum      
Property Plant And Equipment [Line Items]      
Period of review of special costs of assets 96 months    
Chartered-in vessels      
Property Plant And Equipment [Line Items]      
Impairment loss $ 38,636,000