Schedule of Carrying Value of Trust Assets and Obligations Under Supplemental Plan (Detail) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Compensation And Retirement Disclosure [Abstract]
Investments held in Rabbi Trust	[1]	$ 18	$ 8,908
Obligations under the supplemental plan		$ 21,413	$ 32,508

[1] We converted substantially all investments held in the rabbi trust to cash to fund a lump sum benefit to the former CEO in May 2018. Refer to Note (10) for more information regarding this payment