CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (1.9)	$ 40.8	$ (7.8)	$ 146.6
Other comprehensive income (loss), net of tax:
Currency translation	(1.4)	(23.3)	(12.4)	(50.1)
Defined benefit pension plans	0.7	2.3	7.0	7.0
Other	0.0	(0.2)	(0.4)	(0.5)
Total other comprehensive loss, net	(0.7)	(21.2)	(5.8)	(43.6)
Comprehensive income (loss)	(2.6)	19.6	(13.6)	103.0
Comprehensive income attributable to noncontrolling interest	4.0	9.1	6.3	35.6
Comprehensive income (loss) attributable to Valhi stockholders	$ (6.6)	$ 10.5	$ (19.9)	$ 67.4