Pension Benefits - Fair Value of Plan Assets (Details) - Pension Plan - USD ($) $ in Thousands	Dec. 26, 2021	Dec. 27, 2020	Dec. 29, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	$ 1,550,078	$ 1,585,221	$ 1,648,667
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	1,550,078
Recurring | U.S. Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	12,739	28,002
Recurring | International Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	29,453	34,025
Recurring | Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets		29,011
Recurring | Registered Investment Companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	270,662	238,737
Recurring | Common Collective Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	370,042	471,629
Recurring | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	710,413	646,330
Recurring | U.S. Treasury and Other Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	52,520	42,111
Recurring | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	37,922	40,150
Recurring | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	36,630	10,693
Recurring | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	7,229	5,481
Recurring | Private Equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	7,014	9,770
Recurring | Hedge Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	15,454	29,282
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	312,854	329,775
Recurring | Level 1 | U.S. Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	12,739	28,002
Recurring | Level 1 | International Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	29,453	34,025
Recurring | Level 1 | Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets		29,011
Recurring | Level 1 | Registered Investment Companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	270,662	238,737
Recurring | Level 1 | Common Collective Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 1 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 1 | U.S. Treasury and Other Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 1 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 1 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 1 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 1 | Private Equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 1 | Hedge Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	837,485	739,284
Recurring | Level 2 | U.S. Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 2 | International Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 2 | Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets		0
Recurring | Level 2 | Registered Investment Companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 2 | Common Collective Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 2 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	710,413	646,330
Recurring | Level 2 | U.S. Treasury and Other Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	52,520	42,111
Recurring | Level 2 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	37,922	40,150
Recurring | Level 2 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	36,630	10,693
Recurring | Level 2 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 2 | Private Equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 2 | Hedge Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3 | U.S. Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3 | International Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3 | Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets		0
Recurring | Level 3 | Registered Investment Companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3 | Common Collective Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3 | U.S. Treasury and Other Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3 | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3 | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3 | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3 | Private Equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Level 3 | Hedge Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Investment Measured at Net Asset Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	399,739	516,162
Recurring | Investment Measured at Net Asset Value | U.S. Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Investment Measured at Net Asset Value | International Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Investment Measured at Net Asset Value | Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets		0
Recurring | Investment Measured at Net Asset Value | Registered Investment Companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Investment Measured at Net Asset Value | Common Collective Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	370,042	471,629
Recurring | Investment Measured at Net Asset Value | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Investment Measured at Net Asset Value | U.S. Treasury and Other Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Investment Measured at Net Asset Value | Municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Investment Measured at Net Asset Value | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	0	0
Recurring | Investment Measured at Net Asset Value | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	7,229	5,481
Recurring | Investment Measured at Net Asset Value | Private Equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	7,014	9,770
Recurring | Investment Measured at Net Asset Value | Hedge Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Defined benefits plan, plan assets	$ 15,454	$ 29,282