Acquisition of Remaining Joint Venture Interest in LPC - Assets acquired and liabilities assumed (Details) - USD ($) $ in Millions	Jul. 16, 2024	Mar. 31, 2025	Dec. 31, 2024	Jul. 15, 2024
Allocation of purchase price to identifiable assets acquired and liabilities assumed:
Goodwill		$ 382.3	$ 382.3
Louisiana Pigment Company, L.P. (LPC) | Kronos
Consideration:
Cash consideration	$ 185.0
Working capital adjustment	(11.0)
Earn-out liability	4.2
Total fair value of consideration	178.2
Fair value of investment in TiO2 manufacturing joint venture	178.2
Total	356.4
Allocation of purchase price to identifiable assets acquired and liabilities assumed:
Cash and cash equivalents	21.3
Restricted cash	1.3
Accounts and other receivables, net	0.2
Inventories, net	82.0
Prepaid expenses and other	0.6
Other assets	10.7
Property and equipment	268.5
Accounts payable and accrued liabilities	(21.7)
Other noncurrent liabilities	(6.4)
Deferred tax liability	(2.7)
Total net identifiable assets acquired	353.8
Goodwill	2.6
Total	356.4
Goodwill expected to be deductible for tax purposes	$ 0.1
Percentage acquired	50.00%			50.00%
Louisiana Pigment Company, L.P. (LPC) | Kronos | Minimum
Allocation of purchase price to identifiable assets acquired and liabilities assumed:
Property and equipment useful life	5 years
Louisiana Pigment Company, L.P. (LPC) | Kronos | Maximum
Allocation of purchase price to identifiable assets acquired and liabilities assumed:
Property and equipment useful life	20 years