Schedule of Fair Value of Senior Notes (Parenthetical) (Detail) - Recourse Debt	9 Months Ended	12 Months Ended
	Sep. 26, 2015	Dec. 27, 2014
9.75% senior secured notes, due 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, interest rate	9.75%	9.75%
Long-term Debt, due date	2019	2019
7.35% debentures, due 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, interest rate	7.35%	7.35%
Long-term Debt, due date	2016	2016
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
American & Foreign Power Company, Inc. 5% debentures, due 2030
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, interest rate	5.00%	5.00%
Long-term Debt, due date	2030	2030
Carrying Value | 9.75% senior secured notes, due 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, interest rate	9.75%	9.75%
Long-term Debt, due date	2019	2019
Carrying Value | 7.35% debentures, due 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, interest rate	7.35%	7.35%
Long-term Debt, due date	2016	2016
Carrying 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
Carrying Value | American & Foreign Power Company, Inc. 5% debentures, due 2030
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, interest rate	5.00%	5.00%
Long-term Debt, due date	2030	2030