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	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Trading Securities and Other Trading Assets [Line Items]
Net realized gains (losses) from sale of trading securities	$ 143	$ 10	$ 195
Dividend and interest income	419	635	422
Net unrealized holding gains (losses)	1,817	(1,512)	1,002
Net investment income (losses)	$ 2,379	$ (867)	$ 1,619