Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 27, 2015	Dec. 28, 2014	Dec. 29, 2013
Fair Value of Financial Instruments [Abstract]
Fair value of available for sale investments, fair value option	$ 22,539	$ 23,560	$ 28,048
Gain on available for sale investments, fair value option	$ (682)	899	152
Redemption period	45 days
Reconciliation of Level 3 Assets
Balance at beginning of year	$ (19,553)	5,484
Issuance of option agreement	0	(25,590)
Purchases	7,600	0
Sales	(7,924)	0
(Loss) gain from change in fair value	2,809	553
Balance at end of year	(17,068)	(19,553)	$ 5,484
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, assets	26,015	28,042
Derivatives, assets	107,634	69,148
Total assets	133,649	97,190
Derivatives, liabilities	1,240	2,591
Option Agreement	28,360	25,340
Total Liabilities	29,600	27,931
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	3,476	4,482
Derivatives, assets	0	0
Total assets	3,476	4,482
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	11,247	17,773
Derivatives, assets	107,634	69,148
Total assets	118,881	86,921
Derivatives, liabilities	1,240	2,591
Option Agreement	0	0
Total Liabilities	1,240	2,591
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	11,292	5,787
Derivatives, assets	0	0
Total assets	11,292	5,787
Derivatives, liabilities	0	0
Option Agreement	28,360	25,340
Total Liabilities	$ 28,360	$ 25,340