Partnership Distributions Schedule of Cash Distributions Paid to Unitholder (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Nov. 14, 2016
Aug. 12, 2016
May 13, 2016
Feb. 12, 2016
Nov. 13, 2015
Aug. 14, 2015
May 15, 2015
Feb. 13, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Distribution Made to Limited Partner [Line Items]                      
Distribution declared per common and subordinated units (in dollars per share)                 $ 2.22 $ 1.9800 $ 1.7400
Dividends Declared One                      
Distribution Made to Limited Partner [Line Items]                      
Distribution declared per common and subordinated units (in dollars per share)       $ 0.5175       $ 0.4575      
Cash distributions, paid       $ 11,103       $ 9,589      
Dividend Declared Two                      
Distribution Made to Limited Partner [Line Items]                      
Distribution declared per common and subordinated units (in dollars per share)     $ 0.5325       $ 0.4725        
Cash distributions, paid     $ 11,619       $ 9,958        
Dividend Declared Three                      
Distribution Made to Limited Partner [Line Items]                      
Distribution declared per common and subordinated units (in dollars per share)   $ 0.5475       $ 0.4875          
Cash distributions, paid   $ 12,046       $ 10,323          
Dividend Declared Four                      
Distribution Made to Limited Partner [Line Items]                      
Distribution declared per common and subordinated units (in dollars per share) $ 0.5625       $ 0.5025            
Cash distributions, paid $ 12,477       $ 10,699            
Common Stock | Dividends Declared One                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid       5,724       4,981      
Common Stock | Dividend Declared Two                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid     5,981       5,199        
Common Stock | Dividend Declared Three                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid   6,150       5,364          
Common Stock | Dividend Declared Four                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid 6,324       5,533            
Subordinated Units | Dividends Declared One                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid       5,212       4,608      
Subordinated Units | Dividend Declared Two                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid     5,363       4,759        
Subordinated Units | Dividend Declared Three                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid   5,515       4,910          
Subordinated Units | Dividend Declared Four                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid 5,665       5,061            
Incentive Distribution Rights | Dividends Declared One                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid       $ 167       $ 0      
Incentive Distribution Rights | Dividend Declared Two                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid     $ 275       $ 0        
Incentive Distribution Rights | Dividend Declared Three                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid   $ 381       $ 49          
Incentive Distribution Rights | Dividend Declared Four                      
Distribution Made to Limited Partner [Line Items]                      
Cash distributions, paid $ 488       $ 105