Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Fair Value of Financial Instruments [Abstract]
Fair value of available for sale investments, fair value option	$ 24,436	$ 23,571
Gain on available for sale investments, fair value option	$ 1,500	1,010	$ (682)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Redemption period	45 days
Reconciliation of Level 3 Assets
Balance at beginning of year	$ (28,770)	(28,360)
(Loss) gain from change in fair value	4,790	(410)
Balance at end of year	$ (23,980)	(28,770)	$ (28,360)
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Redemption period	30 days
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Redemption period	90 days
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, assets	$ 3,126	3,736
Derivatives, assets	12,226	87,894
Total assets	15,352	91,630
Derivatives, liabilities	23,051	11,309
Option Agreement	23,980	28,770
Total Liabilities	47,031	40,079
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, assets	3,126	3,736
Derivatives, assets	0	0
Total assets	3,126	3,736
Derivatives, liabilities	0	0
Option Agreement	0	0
Total Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, assets	0	0
Derivatives, assets	12,226	87,894
Total assets	12,226	87,894
Derivatives, liabilities	23,051	11,309
Option Agreement	0	0
Total Liabilities	23,051	11,309
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, assets	0	0
Derivatives, assets	0	0
Total assets	0	0
Derivatives, liabilities	0	0
Option Agreement	23,980	28,770
Total Liabilities	$ 23,980	$ 28,770