Schedule of Fair Value of Assets and Liabilities (Detail) - USD ($) $ in Millions	Mar. 27, 2021	Dec. 26, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Company-owned life insurance	$ 138	$ 147
Long-Term Debt | New Facilities loans Under Third Amended Credit Agreement due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	100	100
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Company-owned life insurance	138	147
Carrying Amount | Long-Term Debt | New Facilities loans Under Third Amended Credit Agreement due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	100	100
Revenue bonds, due in varying amounts periodically through 2029 | Long-Term Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	177	177
Revenue bonds, due in varying amounts periodically through 2029 | Carrying Amount | Long-Term Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	176	176
American & Foreign Power Company, Inc. 5% debentures, due 2030 | Long-Term Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	15	14
American & Foreign Power Company, Inc. 5% debentures, due 2030 | Carrying Amount | Long-Term Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 15	$ 15