Investments Held in Rabbi Trust - Components of Investment Income (Losses), Included in Other Income (Expense), Net in Accompanying Consolidated Statements of Operations (Detail) - Other Income (Expense), Net [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net realized gains (losses) from sale of trading securities	$ 50	$ 61
Dividend and interest income	33	29
Net unrealized holding gains (losses)	(2,140)	1,090
Net investment income (losses)	$ (2,057)	$ 1,180