Annual report pursuant to Section 13 and 15(d)

Summary of Potential Number of Units that Could Vest Under Restricted Stock Unit Awards (Detail)

v3.6.0.2
Summary of Potential Number of Units that Could Vest Under Restricted Stock Unit Awards (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Schedule of Restricted Stock Unit [Line Items]      
Number of units at threshold IRR 84,554 47,640 65,832
Number of units at target IRR 169,107 95,282 131,683
Number of units at maximum IRR 253,661 142,917 197,515
Fair value of units at threshold IRR [1] $ 2,522 $ 2,057 $ 1,879
Fair value of units at target IRR [1] 5,044 4,115 3,758
Fair value of units at maximum IRR [1] $ 7,568 $ 6,173 $ 5,637
[1] The grant date fair values for units issued during the years ended December 31, 2014, 2015, and 2016 were $28.54, $43.19 and $29.83, respectively.