Related Party Transactions (Details)
 0 Months Ended 12 Months Ended
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Dec. 16, 2013
Manager
USD ($)
Jan. 02, 2012
Manager
Dec. 16, 2011
Manager
Feb. 08, 2010
Manager
USD ($)
Dec. 31, 2014
Manager
USD ($)
Dec. 31, 2014
Manager
EUR (€)
Dec. 31, 2013
Manager
USD ($)
Dec. 31, 2012
Manager
USD ($)
Dec. 31, 2012
Manager
EUR (€)
Dec. 31, 2014
The Swedish Club
USD ($)
Dec. 31, 2013
The Swedish Club
USD ($)
Dec. 31, 2012
The Swedish Club
USD ($)
Related Party Transactions                            
Adjusted management fees per day for commercial, chartering and administrative services     $ 800     $ 675       $ 850        
Adjusted management fees per vessel per day for vessels on bareboat charter     400     340       425        
Adjusted management fees per vessel per day for vessels on time charter     800     675       850        
Flat management fees per newbuilding vessel for the supervision of newbuilding contracts           725,000                
Management commission on gross freight, charter hire, ballast bonus and demurrage before adjustment (as a percent)     1.00%   0.75%         1.25% 1.25%      
Adjusted management commission on gross freight, charter hire, ballast bonus and demurrage (as a percent)     1.25% 1.00%           0.50% 0.50%      
Fee for providing services of executive officers               1,500,000     1,400,000      
Management commission based on the contract price of any vessel bought or sold (excluding newbuildings) (as a percent)       0.50%                    
Management fees incurred shown under General and administrative expenses             16,300,000   15,000,000 15,500,000        
Management commissions incurred shown under Voyage expenses             7,000,000   5,800,000 5,900,000        
Monthly advances on account of the vessels' operating expenses 10,597,000 14,459,000                        
Premiums paid                       $ 8,500,000 $ 9,600,000 $ 10,400,000