Earnings Per Unit - Calculation of Earnings (Loss) Per Unit (Parenthetical) (Detail)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Earnings Per Unit [Line Items]      
General partner's interest in net income, percentage 0.10% 0.10% 0.10%
Supplemental EPU [Member]      
Earnings Per Unit [Line Items]      
General partner's interest in net income, percentage 0.10% 0.10% 0.10%