Schedule of Debt (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015
Recourse Debt
Debt Instrument [Line Items]
Long term debt, interest rate	5.00%	5.00%
Non-Recourse Debt
Debt Instrument [Line Items]
Long term debt, due date	2019	2019
Long term debt, interest rate	5.42%	5.42%
7.35% debentures, due 2016 | Recourse Debt
Debt Instrument [Line Items]
Long term debt, due date	2016	2016
Long term debt, interest rate	7.35%	7.35%
Senior Secured Notes, due 2019 | Recourse Debt
Debt Instrument [Line Items]
Long term debt, due date	2019	2019
Revenue bonds, due in varying amounts periodically through 2029 | Recourse Debt
Debt Instrument [Line Items]
Long term debt, due date	2029	2029
American & Foreign Power Company, Inc. 5% debentures, due 2030 | Recourse Debt
Debt Instrument [Line Items]
Long term debt, due date	2030	2030
Long term debt, interest rate	5.00%