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Summary of Significant Accounting Policies - Additional Information (Details) |  | 3 Months Ended | 12 Months Ended |
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May 31, 2020 USD ($) | Dec. 31, 2020 USD ($) | Jun. 30, 2020 USD ($) | Dec. 31, 2020 USD ($) a | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Jan. 01, 2019 USD ($)
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Research and development costs |  |  |  |  | $ 15,500,000 | $ 16,000,000.0 | $ 14,400,000 |
Cash and cash equivalents |  |  | $ 974,600,000 |  | 974,600,000 | 679,500,000 |  |
Cash equivalents |  |  | 662,200,000 |  | 662,200,000 | 410,700,000 |  |
Other-than-temporary impairment charges on available-for-sale securities |  |  |  |  | 0 | 0 |  |
Allowance for doubtful accounts |  |  | 3,000,000.0 |  | $ 3,000,000.0 | 3,000,000.0 |  |
Customer returns, allowances and earned discounts as a percentage of gross selling price |  |  |  |  | 1.00% |  |  |
Reserve for customer accounts receivable, percentage |  |  |  |  | 1.00% |  |  |
Reserve for customer deductions |  |  |  |  | $ 7,600,000 | 8,400,000 |  |
Interest capitalization, construction in progress |  |  |  |  | 3,700,000 | 3,400,000 | 4,500,000 |
Depreciation expense |  |  |  |  | 362,500,000 | 346,800,000 | 361,700,000 |
Incremental depreciation |  |  |  |  | $ 4,500,000 | $ 300,000 | 14,500,000 |
Intangible asset, useful life, in years |  |  |  |  | 9 years 1 month 6 days | 9 years 10 months 24 days |  |
Goodwill |  |  | 863,500,000 |  | $ 863,500,000 | $ 918,700,000 | 917,300,000 |
Goodwill and intangible asset impairment |  |  |  |  | 0 | 0 | 0 |
Goodwill impairment |  |  | 0 |  | 55,200,000 |  |  |
Deferred financing costs |  |  | 14,300,000 |  | $ 14,300,000 | 16,300,000 |  |
Area leased under timberland cutting rights (acres) | a |  |  |  |  | 71,000 |  |  |
Depletion expense |  |  |  |  | $ 3,100,000 | 2,700,000 | 7,600,000 |
Software amortization expense |  |  |  |  | 1,100,000 | 900,000 | 2,100,000 |
Cloud computing arrangements |  |  | 4,000,000.0 |  | 4,000,000.0 |  |  |
Operating lease liabilities |  |  | 242,500,000 |  | 242,500,000 | 240,200,000 |  |
Other long-term assets |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Long-term lease costs capitalization (Cutting rights) |  |  | 20,300,000 |  | 20,300,000 | 21,600,000 |  |
Net capitalized software costs |  |  | 4,800,000 |  | $ 4,800,000 | 1,400,000 |  |
Adjustments for New Accounting Pronouncement | Long-term debt |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Deferred financing costs |  |  |  |  |  | $ 14,300,000 | 16,300,000 |
ASU 2016-02 |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Operating lease liabilities |  |  |  |  |  |  |  | $ 228,000,000
Paper Reporting Unit |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Goodwill impairment |  | $ 55,200,000 |  | $ 55,200,000 |  |  |  |
Customer Relationships |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Intangible asset, useful life, in years | [1],[2] |  |  |  | 9 years 1 month 6 days | 10 years |  |
Trademarks and Trade Names |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Intangible asset, useful life, in years |  |  |  |  | 9 years 3 months 18 days | 9 years 6 months |  |
Paper |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Recoverability test results recoverable percentage |  | 100.00% |  |  |  |  |  |
Goodwill |  |  | 0 |  | $ 0 | $ 55,200,000 | $ 55,200,000 |
Goodwill impairment |  |  |  |  | $ 55,200,000 |  |  |
Minimum |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Term of senior credit facilities and notes, in years |  |  |  |  | 10 years |  |  |
Minimum | Customer Relationships |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Intangible asset, useful life, in years |  |  |  |  | 10 years |  |  |
Minimum | Trademarks and Trade Names |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Intangible asset, useful life, in years |  |  |  |  | 5 years |  |  |
Maximum |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Term of senior credit facilities and notes, in years |  |  |  |  | 30 years |  |  |
Maximum | Customer Relationships |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Intangible asset, useful life, in years |  |  |  |  | 40 years |  |  |
Maximum | Trademarks and Trade Names |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Intangible asset, useful life, in years |  |  |  |  | 20 years |  |  |
Foreign operations |  |  |  |  |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |  |  |  |  |
Cash and cash equivalents |  |  | $ 2,200,000 |  | $ 2,200,000 | $ 2,400,000 |  |
[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] | During the second quarter of 2020, the Company recorded a $4.5 million adjustment to decrease the remaining book value of the customer relationships intangible asset as a result of the closure of the San Lorenzo, California corrugated products facility.

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