CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 29.7	$ (0.3)	$ 43.3	$ (4.9)
Other comprehensive income (loss), net of tax:
Currency translation	1.6	(4.9)	(16.7)	(11.0)
Defined benefit pension plans	0.7	5.6	1.4	6.3
Other	(0.1)	(0.2)	(0.2)	(0.4)
Total other comprehensive income (loss), net	2.2	0.5	(15.5)	(5.1)
Comprehensive income (loss)	31.9	0.2	27.8	(10.0)
Comprehensive income attributable to noncontrolling interest	10.4	2.6	11.6	2.3
Comprehensive income (loss) attributable to Valhi stockholders	$ 21.5	$ (2.4)	$ 16.2	$ (12.3)