CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 13.6	$ (3.7)
Other comprehensive income (loss), net of tax:
Currency translation	(18.3)	(6.1)
Defined benefit pension plans	0.7	0.7
Other	(0.1)	(0.2)
Total other comprehensive loss, net	(17.7)	(5.6)
Comprehensive loss	(4.1)	(9.3)
Comprehensive income (loss) attributable to noncontrolling interest	1.2	(0.3)
Comprehensive loss attributable to Valhi stockholders	$ (5.3)	$ (9.0)