Acquisitions - Additional Information (Details) - USD ($) $ in Millions			1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 09, 2018	Oct. 02, 2017	Oct. 31, 2017	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Cash purchase price					$ 56.3	$ 273.8	$ 485.4
Englander
Business Acquisition [Line Items]
Acquisition completion date	Oct. 09, 2018
Cash purchase price	$ 56.3
Goodwill	28.6
Intangible assets	$ 14.1
Acquired finite-lived intangible assets, weighted average useful life	9 years 8 months 12 days
Northern Sheets LLC And Central California Sheets LLC
Business Acquisition [Line Items]
Percentage of membership interests acquired			100.00%
Sacramento Container Corporation
Business Acquisition [Line Items]
Acquisition completion date			Oct. 31, 2017
Cash purchase price			$ 274.0
Acquired finite-lived intangible assets, weighted average useful life		9 years 7 months 6 days
Adjustment to final valuation of intangible assets				$ 5.5	5.5
Decrease in other intangible assets with an offset to goodwill				$ (5.5)	$ (5.5)
Sacramento Container Corporation | Minimum
Business Acquisition [Line Items]
Property, plant and equipment useful life		1 year
Sacramento Container Corporation | Maximum
Business Acquisition [Line Items]
Property, plant and equipment useful life		13 years