Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Abstract]
Measurement period adjustment			$ 4.4
Income from operations before provision for taxes [Abstract]
Domestic	$ 21.4	$ 46.9	93.1
Foreign	116.6	110.4	111.0
Income from operations before tax and equity in earnings	138.0	157.3	204.1
Domestic [Abstract]
Taxes currently payable, Federal	(7.1)	(3.3)	(3.7)
Taxes currently payable, State and local	0.2	0.8	1.4
Deferred income taxes	2.2	(6.6)	11.1
Domestic tax provision (benefit)	(4.7)	(9.1)	8.8
Foreign [Abstract]
Taxes currently payable	34.0	26.7	21.3
Deferred income taxes	(4.9)	5.2	4.3
Foreign tax provision	29.1	31.9	25.6
Total tax provision (benefit)	$ 24.4	$ 22.8	$ 34.4
Reconciliation of U.S. federal statutory tax rate to effective tax rate [Abstract]
U.S. statutory rate	21.00%	21.00%	21.00%
Depletion	(6.20%)	(5.00%)	(3.90%)
Difference between tax provided on foreign earnings and the U.S. statutory rate	3.30%	3.80%	1.10%
Global Intangible Low-Tax Income (GILTI)	0.40%	0.00%	0.80%
Foreign Derived Intangible Income	(1.00%)	(0.80%)	(0.70%)
State and local taxes, net of federal tax benefit	0.00%	0.20%	1.90%
Tax credits and foreign dividends	(0.60%)	(0.70%)	(0.30%)
Change in valuation allowance	0.00%	1.00%	0.00%
Impact of uncertain tax positions	(0.20%)	(5.00%)	0.50%
Impact of officer's non-deductible compensation	1.00%	0.80%	0.80%
Impact of U.S. Tax Reform	0.00%	(1.10%)	(2.20%)
Other	0.00%	0.30%	(2.10%)
Consolidated effective tax rate	17.70%	14.50%	16.90%
Deferred tax assets attributable to [Abstract]
Accrued liabilities	$ 29.8	$ 29.7
Net operating loss carry forwards	31.1	33.9
Pension and post-retirement benefits costs	46.3	39.0
Other	28.2	31.4
Valuation allowance	(20.9)	(23.8)
Total deferred tax assets	114.5	110.2
Deferred tax liabilities attributable to [Abstract]
Plant and equipment, principally due to differences in depreciation	169.5	181.3
Intangible assets	69.5	69.5
Other	13.9	17.0
Total deferred tax liabilities	252.9	267.8
Net deferred tax asset (liability), long-term	(138.4)	(157.6)
Current and long-term portion of net deferred tax assets [Abstract]
Net deferred tax asset, long-term	25.3	23.0
Net deferred tax liability, long-term	163.7	180.6
Net deferred tax asset (liability), long-term	(138.4)	(157.6)
Operating loss carryforwards [Abstract]
Deferred tax assets arising from tax loss carry forwards which will be realized through future operations	31.1
Unrecognized tax benefits [Abstract]
Unrecognized tax benefits that would impact effective tax rate	5.1
Unrecognized tax benefits [Roll forward]
Balance at beginning of the year	7.9	16.6
Increases related to current year tax positions	0.7	1.5
Increases related to new judgments	0.0	0.7
Decreases related to audit settlements and statute expirations	(1.0)	(10.9)
Balance at the end of the year	7.6	7.9	$ 16.6
Income Tax Penalties and Interest Expense [Abstract]
Unrecognized tax benefits, interest and penalties	0.0
Unrecognized tax benefits, accrued interest and penalties	1.9
Cash paid for income taxes [Abstract]
Net cash Income taxes paid	28.5	$ 29.5	$ 43.8
Undistributed earnings of foreign subsidiaries [Abstract]
Foreign subsidiaries' undistributed earnings	460.1
Deferred tax liabilities with respect to foreign withholding taxes or state taxes have been recognized	0.0
Finite lived tax loss carry forwards [Member]
Operating loss carryforwards [Abstract]
Deferred tax assets arising from tax loss carry forwards which will be realized through future operations	$ 17.6
Expiration period	20 years
Indefinite lived tax loss carry forwards [Member]
Operating loss carryforwards [Abstract]
Deferred tax assets arising from tax loss carry forwards which will be realized through future operations	$ 13.5