Compensation Expense Associated with Performance Units (Detail) - Performance Units Awards - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense associated with Performance Units	$ 830
2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense associated with Performance Units	667	$ 667
2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense associated with Performance Units	$ 482	482
2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense associated with Performance Units		$ 321