Schedule of Fair Value of Senior Notes (Parenthetical) (Detail)		12 Months Ended
	Sep. 15, 2016	Dec. 31, 2016	Dec. 26, 2015
Recourse Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, interest rate		5.00%	5.00%
9.75% senior secured notes, due 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, interest rate	9.75%
Long-term debt, due date	2019
9.75% senior secured notes, due 2019 | Recourse Debt | Carrying Value
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
9.75% senior secured notes, due 2019 | Recourse Debt | Fair Value
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 | Recourse Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, interest rate		7.35%	7.35%
7.35% debentures, due 2016 | Recourse Debt | Carrying Value
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
7.35% debentures, due 2016 | Recourse Debt | Fair Value
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 | Recourse Debt | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, due date		2029	2029
Revenue bonds, due in varying amounts periodically through 2029 | Recourse Debt | Fair Value
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 | Recourse Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, interest rate		5.00%
American & Foreign Power Company, Inc. 5% debentures, due 2030 | Recourse Debt | Carrying Value
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
American & Foreign Power Company, Inc. 5% debentures, due 2030 | Recourse Debt | Fair Value
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