Restructuring and Other Items, net (Details) $ in Millions	3 Months Ended			12 Months Ended
	Oct. 03, 2021 USD ($)	Sep. 27, 2020 USD ($)	Jun. 28, 2020 USD ($) Mill	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Restructuring Charges [Abstract]
Asset write-down charges				$ 0.0	$ 0.7	$ 7.1
Severance and other related costs				0.0	0.4	0.5
Total restructuring and other items, net				0.0	1.1	7.6
Restructuring Liability [Roll Forward]
Restructuring liability, beginning of period				2.2	3.6
Additional provisions				0.0	0.1
Cash payments				(0.7)	(1.5)
Other				(1.5)	0.0
Restructuring liability, end of period				0.0	2.2	3.6
Specialty Minerals [Member]
Restructuring Charges [Abstract]
Asset write-down charges				0.0	0.7	7.1
Severance and other related costs				$ 0.0	$ 0.4	$ 0.5
Specialty Minerals [Member] | Paper PCC [Member]
Restructuring and Other Items, Net [Abstract]
Number of mills with lease terminations | Mill			1
Restructuring Charges [Abstract]
Asset write-down charges	$ 0.7	$ 1.1	$ 6.0
Severance and other related costs	$ 0.4		$ 0.3
Verso Papers [Member]
Restructuring and Other Items, Net [Abstract]
Number of paper mills being idled indefinitely | Mill			2