XML 117 R89.htm IDEA: XBRL DOCUMENT v3.8.0.1
Long-Term Compensation - Assumptions Used for Each Grant Based on Year Granted (Detail) - POP LTIP Units [Member] - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Risk free interest rate 1.49% 0.99% 0.86%
Expected volatility 22.20% 20.50% 28.00%
Aggregate fair value $ 20,400 $ 26,600 $ 26,500