Annual report pursuant to Section 13 and 15(d)

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

v3.19.3.a.u2
Summary of Potential Number of Units that Could Vest Under Restricted Stock Unit Awards (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disclosure Of Restricted Stock Unit [Abstract]      
Number of units at threshold IRR 136,285 76,065 58,545
Number of units at target IRR 204,427 152,129 117,089
Number of units at maximum IRR 306,651 228,194 175,634
Fair value of units at threshold IRR [1] $ 5,011 $ 2,967 $ 2,481
Fair value of units at target IRR [1] 7,517 5,938 4,961
Fair value of units at maximum IRR [1] $ 11,276 $ 8,906 $ 7,442
[1] The grant date fair value for units issued during the year ended December 31, 2017 was $42.37. The grant date fair values for the units issued during the year ended December 31, 2018  ranged from $37.55 to $39.03.  The grant date fair value for units issued during the year ended December 31, 2019