Acquisitions - Summary of Weighted Average Life and Fair Value of Intangible Asset Recognized in KapStone Acquisition, Excluding Goodwill (Details) - KapStone Acquisition [Member] $ in Millions	Nov. 02, 2018 USD ($)
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	11 years 10 months 24 days
Gross Carrying Amount	$ 1,366.4
Customer Relationships [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	11 years 8 months 12 days
Gross Carrying Amount	$ 1,303.0
Trademarks and Tradenames [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	16 years 10 months 24 days
Gross Carrying Amount	$ 54.2
Favorable Contracts [Member]
Acquired Finite Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Useful Life	6 years
Gross Carrying Amount	$ 9.2