Schedule of Fair Value of Assets and Liabilities (Parenthetical) (Detail) - Recourse Debt	6 Months Ended	12 Months Ended
	Jun. 27, 2020	Dec. 28, 2019
Carrying Amount | Revolving credit facility, due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, due date	2025	2025
Carrying Amount | Term Loan, due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, due date	2022	2022
Carrying Amount | Revenue bonds, due in varying amounts periodically through 2029
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, due date	2029	2029
Carrying Amount | American & Foreign Power Company, Inc. 5% debentures, due 2030
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, due date	2030	2030
Long-term debt, interest rate	5.00%	5.00%
Fair Value | Revolving credit facility, due 2025
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, due date	2025	2025
Fair Value | Term Loan, due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, due date	2022	2022
Fair Value | Revenue bonds, due in varying amounts periodically through 2029
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, due date	2029	2029
Fair Value | American & Foreign Power Company, Inc. 5% debentures, due 2030
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, due date	2030	2030
Long-term debt, interest rate	5.00%	5.00%