Unitholders' Equity (Details) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 12 Months Ended
Jun. 16, 2015
Jun. 11, 2015
May 19, 2015
Dec. 10, 2014
Dec. 05, 2014
Jun. 30, 2015
Dec. 31, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Number of common units sold           3,000,000 3,565,000   3,000,000 3,565,000
Net proceeds from public offering after deducting underwriting fees and offering expenses $ 109,300     $ 137,800         $ 109,305 $ 137,844
At The Market Offering Program                    
Number of common units sold               0 0  
Common units                    
Number of common units sold   3,000,000     3,565,000       3,000,000 3,565,000
Common units issued in public offering, offer price (in dollars per share)   $ 38.12     $ 40.24          
Common units | At The Market Offering Program                    
Aggregate offering price     $ 50,000