Goodwill and Intangible Assets - Components of Intangible Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (in Years)		9 years 10 months 24 days	10 years 9 months 18 days
Gross Carrying Amount		$ 542.9	$ 543.7
Accumulated Amortization		$ 204.1	$ 165.5
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (in Years)	[1],[2]	10 years	10 years 10 months 24 days
Gross Carrying Amount	[1],[2]	$ 503.8	$ 504.6
Accumulated Amortization	[1],[2]	$ 180.2	$ 144.5
Trademarks and Trade Names
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (in Years)	[2]	9 years 6 months	10 years 1 month 6 days
Gross Carrying Amount	[2]	$ 34.8	$ 34.8
Accumulated Amortization	[2]	$ 20.6	$ 18.3
Other Intangible Assets
Finite Lived Intangible Assets [Line Items]
Weighted Average Remaining Useful Life (in Years)	[2]	2 years 1 month 6 days	3 years
Gross Carrying Amount	[2]	$ 4.3	$ 4.4
Accumulated Amortization	[2]	$ 3.3	$ 2.7

[1] During 2019, a corrugated products facility sold part of its operations which included existing inventory, certain production equipment, and customer relationships corresponding to the operations sold. As a result, the gross carrying amount for the customer relationships intangible asset was decreased by $0.7 million.

[2] In connection with the October 2018 acquisition of Englander, the Company recorded intangible assets of $13.2 million for customer relationships, $0.8 million for trade names, and $0.1 million for other intangibles