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Employee Benefit Plans and Other Postretirement Benefits (Tables) | 12 Months Ended
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Dec. 31, 2023
Retirement Benefits [Abstract] |
Schedule of Obligations and Funded Status of Defined Benefit Pension and Postretirement Benefit Plans | The following table, which includes only company-sponsored defined benefit and other postretirement benefit plans, reconciles the beginning and ending balances of the projected benefit obligation and the fair value of plan assets. We recognize the underfunded status of these plans on the Consolidated Balance Sheets, and we recognize changes in funded status in the year changes occur through the Consolidated Statements of Comprehensive Income (dollars in millions):
|  | Pension Plans |  |  | Postretirement Plans |
|  | Year Ended December 31 |  |  | Year Ended December 31 |
|  | 2023 |  |  | 2022 |  |  | 2023 |  |  | 2022 |
Change in Benefit Obligation: |  |  |  |  |  |  |  |  |  |  |  |
Benefit obligation at beginning of period |  | $ | 1,167.1 |  |  | $ | 1,503.8 |  |  | $ | 9.5 |  |  | $ | 13.6 |
Service cost |  |  | 14.1 |  |  |  | 19.3 |  |  |  | 0.2 |  |  |  | 0.2 |
Interest cost |  |  | 55.8 |  |  |  | 34.7 |  |  |  | 0.5 |  |  |  | 0.3 |
Plan amendments |  |  | 2.9 |  |  |  | 15.1 |  |  |  | — |  |  |  | — |
Actuarial loss (gain) (a) |  |  | 23.3 |  |  |  | (348.0 | ) |  |  | 1.5 |  |  |  | (3.4 | )
Participant contributions |  |  | — |  |  |  | — |  |  |  | 0.4 |  |  |  | 0.5 |
Benefits paid |  |  | (61.1 | ) |  |  | (57.8 | ) |  |  | (1.6 | ) |  |  | (1.7 | )
Benefit obligation at plan year end |  | $ | 1,202.1 |  |  | $ | 1,167.1 |  |  | $ | 10.5 |  |  | $ | 9.5 |
Accumulated benefit obligation portion of above |  | $ | 1,173.3 |  |  | $ | 1,131.0 |  |  |  |  |  |  |
Change in Fair Value of Plan Assets: |  |  |  |  |  |  |  |  |  |  |  |
Plan assets at fair value at beginning of period |  | $ | 1,055.3 |  |  | $ | 1,382.7 |  |  | $ | — |  |  | $ | — |
Actual return on plan assets |  |  | 115.9 |  |  |  | (320.9 | ) |  |  | — |  |  |  | — |
Company contributions |  |  | 51.5 |  |  |  | 51.3 |  |  |  | 1.2 |  |  |  | 1.2 |
Participant contributions |  |  | — |  |  |  | — |  |  |  | 0.4 |  |  |  | 0.5 |
Benefits paid |  |  | (61.1 | ) |  |  | (57.8 | ) |  |  | (1.6 | ) |  |  | (1.7 | )
Fair value of plan assets at plan year end |  | $ | 1,161.6 |  |  | $ | 1,055.3 |  |  | $ | — |  |  | $ | — |
Underfunded status |  | $ | (40.5 | ) |  | $ | (111.8 | ) |  | $ | (10.5 | ) |  | $ | (9.5 | )
Amounts Recognized on Consolidated Balance Sheets: |  |  |  |  |  |  |  |  |  |  |  |
Noncurrent assets |  | $ | 26.5 |  |  | $ | — |  |  | $ | — |  |  | $ | — |
Current liabilities |  |  | (1.7 | ) |  |  | (1.9 | ) |  |  | (0.5 | ) |  |  | (0.5 | )
Noncurrent liabilities |  |  | (65.3 | ) |  |  | (109.9 | ) |  |  | (10.0 | ) |  |  | (9.0 | )
Accrued obligation recognized at December 31 |  | $ | (40.5 | ) |  | $ | (111.8 | ) |  | $ | (10.5 | ) |  | $ | (9.5 | )
Amounts Recognized in Accumulated Other Comprehensive Loss (Income) (Pre-Tax): |  |  |  |  |  |  |  |  |  |  |  |
Prior service cost (credit) |  | $ | 29.2 |  |  | $ | 31.5 |  |  | $ | (3.8 | ) |  | $ | (4.2 | )
Actuarial loss (gain) |  |  | 116.0 |  |  |  | 155.6 |  |  |  | (4.7 | ) |  |  | (6.7 | )
Total |  | $ | 145.2 |  |  | $ | 187.1 |  |  | $ | (8.5 | ) |  | $ | (10.9 | )
(a) For the year ended December 31, 2023, the most significant driver of the increase in aggregate benefit obligations for the pension and OPEB plans was the actuarial losses due to a decrease in the discount rate assumption, PCA Hourly Pension Plan benefit multiplier increases, and changes in salary scale and medical claims assumptions to better reflect anticipated future experience. For the year ended December 31, 2022, the most significant driver of the decrease in aggregate benefit obligations for the pension and OPEB plans was the actuarial gains due to an increase in the discount rate assumption.
Components of Net Periodic Benefit Costs and Other Comprehensive (Income) Loss (Pretax) | The components of net periodic benefit cost and other comprehensive (income) loss (pretax) were as follows (dollars in millions):
|  | Pension Plans |  |  | Postretirement Plans |
|  | Year Ended December 31, |  |  | Year Ended December 31, |
|  | 2023 |  |  | 2022 |  |  | 2021 |  |  | 2023 |  |  | 2022 |  |  | 2021 |
Service cost |  | $ | 14.1 |  |  | $ | 19.3 |  |  | $ | 21.4 |  |  | $ | 0.2 |  |  | $ | 0.2 |  |  | $ | 0.2 |
Interest cost |  |  | 55.8 |  |  |  | 34.7 |  |  |  | 29.6 |  |  |  | 0.5 |  |  |  | 0.3 |  |  |  | 0.3 |
Expected return on plan assets |  |  | (57.1 | ) |  |  | (55.7 | ) |  |  | (63.1 | ) |  |  | — |  |  |  | — |  |  |  | — |
Net amortization of unrecognized amounts: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Prior service cost (credit) |  |  | 5.2 |  |  |  | 3.6 |  |  |  | 3.8 |  |  |  | (0.4 | ) |  |  | (0.4 | ) |  |  | (0.4 | )
Actuarial loss (gain) |  |  | 4.1 |  |  |  | 3.4 |  |  |  | 10.4 |  |  |  | (0.4 | ) |  |  | (0.4 | ) |  |  | (0.5 | )
Net periodic benefit cost |  | $ | 22.1 |  |  | $ | 5.3 |  |  | $ | 2.1 |  |  | $ | (0.1 | ) |  | $ | (0.3 | ) |  | $ | (0.4 | )
Changes in plan assets and benefit obligations recognized in other comprehensive (income) loss: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Actuarial net (gain) loss |  | $ | (35.5 | ) |  | $ | 28.6 |  |  | $ | (82.7 | ) |  | $ | 1.5 |  |  | $ | (3.4 | ) |  | $ | 1.3 |
Prior service cost (credit) |  |  | 2.9 |  |  |  | 15.1 |  |  |  | 2.1 |  |  |  | — |  |  |  | — |  |  |  | (0.1 | )
Amortization of prior service cost (credit) |  |  | (5.2 | ) |  |  | (3.6 | ) |  |  | (3.8 | ) |  |  | 0.4 |  |  |  | 0.4 |  |  |  | 0.4 |
Amortization of actuarial loss (gain) |  |  | (4.1 | ) |  |  | (3.4 | ) |  |  | (10.4 | ) |  |  | 0.4 |  |  |  | 0.4 |  |  |  | 0.5 |
Total recognized in other comprehensive loss (income) (b) |  | $ | (41.9 | ) |  | $ | 36.7 |  |  | $ | (94.8 | ) |  | $ | 2.3 |  |  | $ | (2.6 | ) |  | $ | 2.1 |
Total recognized in net periodic benefit cost and other comprehensive loss (income) (pre-tax) |  | $ | (19.8 | ) |  | $ | 42.0 |  |  | $ | (92.7 | ) |  | $ | 2.2 |  |  | $ | (2.9 | ) |  | $ | 1.7 |
(b) Accumulated losses in excess of 10% of the greater of the projected benefit obligation or the market-related value of assets will be recognized on a straight-line basis over the average remaining service period of active employees in PCA plans (which is between six and nine years) and over the average remaining lifetime of inactive participants in the Boise plan (which is approximately 23 years), to the extent that losses are not offset by gains in subsequent years.
Weighted-Average Assumptions Used To Determine Benefit Obligations and Net Periodic Benefit Cost | The following table presents the assumptions used in the measurement of our benefits obligations:
|  | Pension Plans |  | Postretirement Plans
|  | December 31, |  | December 31,
|  | 2023 |  | 2022 |  | 2021 |  | 2023 |  | 2022 |  | 2021
Weighted-Average Assumptions Used to Determine Benefit Obligations at December 31: |  |  |  |  |  |  |  |  |  |  |  |
Discount rate |  | 4.86 % |  | 5.06 % |  | 2.89 % |  | 4.90 % |  | 5.07 % |  | 2.91 %
Rate of compensation increase |  | 4.75 % |  | 4.00 % |  | 4.00 % |  | N/A |  | N/A |  | N/A
Weighted-Average Assumptions Used to Determine Net Periodic Benefit Cost for the Years Ended December 31: |  |  |  |  |  |  |  |  |  |  |  |
Discount rate |  | 5.06 % |  | 2.89 % |  | 2.57 % |  | 5.07 % |  | 2.92 % |  | 2.60 %
Expected return on plan assets |  | 5.52 % |  | 4.08 % |  | 4.91 % |  | N/A |  | N/A |  | N/A
Rate of compensation increase |  | 4.75 % |  | 4.00 % |  | 4.00 % |  | N/A |  | N/A |  | N/A
Assumed Health Care Cost Trend Rates For Postretirement Benefits | Health Care Cost Trend Rate Assumptions. PCA assumed health care cost trend rates for its postretirement benefits plans were as follows:
|  | 2023 |  | 2022 |  | 2021
Health care cost trend rate assumed for next year |  | 7.13 % |  | 7.24 % |  | 6.55 %
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) |  | 4.44 % |  | 4.42 % |  | 4.50 %
Year that the rate reaches the ultimate trend rate |  | 2033 |  | 2033 |  | 2030
Schedule of Pension Plans' Assets Investment Policies and Strategies | Assets of our pension plans were invested in the following classes of securities at December 31, 2023 and 2022:
|  | Percentage of Fair Value at December 31, |
|  | 2023 |  |  | 2022 |
Fixed income securities |  |  | 72 | % |  |  | 77 | %
International equity securities |  |  | 15 | % |  |  | 13 | %
Domestic equity securities |  |  | 11 | % |  |  | 9 | %
Other |  |  | 2 | % |  |  | 1 | %
Schedule of Fair Value Measurements of Plan Assets by Major Asset Category | The following tables set forth, by level within the fair value hierarchy, discussed in Note 2, Summary of Significant Accounting Policies, the pension plan assets, by major asset category, at fair value at December 31, 2023 and 2022 (dollars in millions):
|  | Fair Value Measurements at December 31, 2023 |
Asset Category |  | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  | Significant Other Observable Inputs (Level 2) |  |  | Significant Unobservable Inputs (Level 3) |  |  | Net Asset Value (NAV) (a) |  |  | Total |
Short-term investments |  | $ | — |  |  | $ | 12.2 |  |  | $ | — |  |  | $ | — |  |  | $ | 12.2 |
Common/collective trust funds: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
International equities |  |  | 96.4 |  |  |  | 53.7 |  |  |  | — |  |  |  | 29.7 |  |  |  | 179.8 |
Domestic equities |  |  | — |  |  |  | 130.4 |  |  |  | — |  |  |  | — |  |  |  | 130.4 |
Corporate and government bonds: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  |  | — |  |  |  | 362.2 |  |  |  | — |  |  |  | — |  |  |  | 362.2 |
Government bonds and agencies |  |  | — |  |  |  | 297.5 |  |  |  | — |  |  |  | — |  |  |  | 297.5 |
Fixed income |  |  | — |  |  |  | 160.7 |  |  |  | — |  |  |  | — |  |  |  | 160.7 |
Municipal bonds |  |  | — |  |  |  | 12.7 |  |  |  | — |  |  |  | — |  |  |  | 12.7 |
Private equity securities |  |  | — |  |  |  | — |  |  |  | — |  |  |  | 0.8 |  |  |  | 0.8 |
Total securities at fair value |  | $ | 96.4 |  |  | $ | 1,029.4 |  |  | $ | — |  |  | $ | 30.5 |  |  | $ | 1,156.3 |
Accrued income |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5.3 |
Total fair value of plan assets |  |  |  |  |  |  |  |  |  |  |  |  |  | $ | 1,161.6 |
|  | Fair Value Measurements at December 31, 2022 |
Asset Category |  | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  | Significant Other Observable Inputs (Level 2) |  |  | Significant Unobservable Inputs (Level 3) |  |  | Net Asset Value (NAV) (a) |  |  | Total |
Short-term investments |  | $ | — |  |  | $ | 9.9 |  |  | $ | — |  |  | $ | — |  |  | $ | 9.9 |
Common/collective trust funds: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
International equities |  |  | 73.3 |  |  |  | 42.4 |  |  |  | — |  |  |  | 16.9 |  |  |  | 132.6 |
Domestic equities |  |  | — |  |  |  | 98.2 |  |  |  | — |  |  |  | — |  |  |  | 98.2 |
Corporate and government bonds: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Corporate bonds |  |  | — |  |  |  | 338.5 |  |  |  | — |  |  |  | — |  |  |  | 338.5 |
Fixed income |  |  | — |  |  |  | 282.6 |  |  |  | — |  |  |  | — |  |  |  | 282.6 |
Government bonds and agencies |  |  | — |  |  |  | 167.1 |  |  |  | — |  |  |  | — |  |  |  | 167.1 |
Municipal bonds |  |  | — |  |  |  | 21.4 |  |  |  | — |  |  |  | — |  |  |  | 21.4 |
Private equity securities |  |  | — |  |  |  | — |  |  |  | — |  |  |  | 1.0 |  |  |  | 1.0 |
Total securities at fair value |  | $ | 73.3 |  |  | $ | 960.1 |  |  | $ | — |  |  | $ | 17.9 |  |  | $ | 1,051.3 |
Accrued income |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.0 |
Total fair value of plan assets |  |  |  |  |  |  |  |  |  |  |  |  |  | $ | 1,055.3 |
(a) In accordance with ASC 820, Fair Value Measurement, certain investments that do not have readily determinable fair values are measured at fair value using the net asset value (NAV) per share practical expedient and are not classified within the fair value hierarchy.
Schedule of Estimated Benefit Payments | The following are estimated benefit payments to be paid to current plan participants by year (dollars in millions). Qualified pension benefit payments are paid from plan assets, while nonqualified pension benefit payments are paid by the Company.
|  | Pension Plans |  |  | Postretirement Plans |
2024 |  | $ | 66.3 |  |  | $ | 0.5 |
2025 |  |  | 70.0 |  |  |  | 0.6 |
2026 |  |  | 73.3 |  |  |  | 0.6 |
2027 |  |  | 76.0 |  |  |  | 0.6 |
2028 - 2033 |  |  | 492.7 |  |  |  | 3.8 |

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- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. Also includes tabular disclosure of the changes in plan assets and benefit obligations recognized in other comprehensive income (loss) during the period. + References No definition available. + Details
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- Definition Tabular disclosure of assets, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, by class that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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- Definition Tabular disclosure of the major categories of plan assets of pension plans and/or other employee benefit plans. This information may include, but is not limited to, the target allocation of plan assets, the fair value of each major category of plan assets, and the level within the fair value hierarchy in which the fair value measurements fall. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (d)(5) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of assumption used to determine benefit obligation and net periodic benefit cost of defined benefit plan. Includes, but is not limited to, discount rate, rate of compensation increase, expected long-term rate of return on plan assets and interest crediting rate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (k) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of benefits expected to be paid by pension plans and/or other employee benefit plans in each of the next five fiscal years and in the aggregate for the five fiscal years thereafter. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (f) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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- Definition Tabular disclosure of the assumed health care cost trend rates for the next year used to measure the expected cost of benefits covered by the plans, including the ultimate trend rate(s) and when that rate is expected to be achieved. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -SubTopic 20 -Subparagraph (l) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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