Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2015	Jun. 29, 2014	Jun. 28, 2015	Jun. 29, 2014	Dec. 28, 2014
Fair Value of Financial Instruments (Thousands of Dollars) [Abstract]
Fair Value of Available for Sale Investments, Fair Value Option	$ 32,766	$ 33,528	$ 32,766	$ 33,528	$ 23,560
Net Gain (Loss) on Available-for-Sale Investments, Fair Value Option	(87)	1,063	(70)	2,240
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, assets	38,725	40,712	38,725	40,712	28,042
Derivatives, assets	105,906	533	105,906	533	69,148
Total assets, fair value hierarchy	144,631	41,245	144,631	41,245	97,190
Derivatives, liabilities	2,748	16,131	2,748	16,131	2,591
Option Agreement	25,190		25,190		25,340
Total Liabilities	27,938		27,938		27,931
Reconciliation of fair value for Level 3 financial instruments
Balance at beginning of year			(19,553)	5,484
Purchases			5,000	0
Gain (loss) from change in fair value			352	133
Balance at end of period	(14,201)	5,617	(14,201)	5,617
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	5,959	7,183	5,959	7,183	4,482
Derivatives, assets	0	0	0	0	0
Total assets, fair value hierarchy	5,959	7,183	5,959	7,183	4,482
Derivatives, liabilities	0	0	0	0	0
Option Agreement	0		0		0
Total Liabilities	0		0		0
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	21,777	27,912	21,777	27,912	17,773
Derivatives, assets	105,906	533	105,906	533	69,148
Total assets, fair value hierarchy	127,683	28,445	127,683	28,445	86,921
Derivatives, liabilities	2,748	16,131	2,748	16,131	2,591
Option Agreement	0		0		0
Total Liabilities	2,748		2,748		2,591
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, assets	10,989	5,617	10,989	5,617	5,787
Derivatives, assets	0	0	0	0	0
Total assets, fair value hierarchy	10,989	5,617	10,989	5,617	5,787
Derivatives, liabilities	0	$ 0	0	$ 0	0
Option Agreement	25,190		25,190		25,340
Total Liabilities	$ 25,190		$ 25,190		$ 25,340