Income Taxes - Component of Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Expected tax expense (benefit), at U.S. federal statutory income tax rate of 21%	$ 3,400	$ (200)
Rate differences on equity in earnings of Kronos, net of dividends	(1,000)	(3,200)
Nontaxable income	(600)
Nondeductible expenses	500
U.S. state income taxes and other, net	200	100
Income tax expense (benefit)	$ 2,505	$ (3,263)