Income Taxes - Component of Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Expected tax expense (benefit), at U.S. federal statutory income tax rate of 35% in 2016 and 2017 and 21% in 2018	$ (11,400)	$ 39,300	$ 4,900
Rate differences on equity in earnings of Kronos	(5,000)	(7,400)	(7,400)
Change in federal tax rate, net	800	(37,500)
U.S. state income taxes and other, net	200		(300)
Income tax benefit	$ (15,361)	$ (5,634)	$ (2,777)