Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Income tax expense	$ 16.9	$ 17.8	$ 60.9	$ 41.4
Income before income taxes and equity income of unconsolidated entity	$ 86.8	$ 139.5	$ 294.6	271.1
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Amount				(11.0)
Discrete tax benefit, reduction of long-term deferred tax liability				2.0
Artistic Carton Company
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Amount				$ (4.0)
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward					$ 168.0