CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 63.4	$ 24.5
Other comprehensive income (loss), net of tax:
Currency translation	5.8	1.7
Defined benefit pension plans	2.4	3.4
Other	(0.2)	(0.2)
Total other comprehensive income (loss), net	8.0	4.9
Comprehensive income	71.4	29.4
Comprehensive income attributable to noncontrolling interest	20.1	11.0
Comprehensive income attributable to Valhi stockholders	$ 51.3	$ 18.4