Quarterly report pursuant to Section 13 or 15(d)

Selected Balance Sheet Data - Summary of Net Change in Carrying Value of Assets Held in Rabbi Trust and Deferred Compensation Liability (Detail)

v3.10.0.1
Selected Balance Sheet Data - Summary of Net Change in Carrying Value of Assets Held in Rabbi Trust and Deferred Compensation Liability (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Balance Sheet Related Disclosures [Abstract]        
Increase in the carrying value of the assets held in the rabbi trust $ 176 $ 170 $ 190 $ 369
Increase in the net carrying value of the deferred compensation obligation $ 188 $ 188 $ 188 $ 399