Summary of Significant Accounting Policies - Issuance, dividends (Details) - $ / shares
1 Months Ended 3 Months Ended 12 Months Ended
Jan. 30, 2017
Jun. 30, 2015
May 31, 2015
Dec. 31, 2014
Nov. 30, 2014
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Net Income Per Limited Partner Unit                        
Public offering of common units   3,000,000   3,565,000             3,000,000 3,565,000
General partner ownership interest (as a percent)   0.67% 0.74% 0.74% 0.83%         0.67%    
Quarterly cash distribution declared (in dollars per unit)           $ 0.4625 $ 0.4625 $ 0.4625 $ 0.4625      
Subsequent event                        
Net Income Per Limited Partner Unit                        
Quarterly cash distribution declared (in dollars per unit) $ 0.4625                      
Weighted average                        
Net Income Per Limited Partner Unit                        
General partner ownership interest (as a percent)                     0.70%