Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2014	Sep. 29, 2013	Sep. 28, 2014	Sep. 29, 2013	Dec. 29, 2013
Fair Value of Financial Instruments (Thousands of Dollars) [Abstract]
Fair Value of Available for Sale Investments, Fair Value Option	$ 24,292	$ 23,452	$ 24,292	$ 23,452	$ 28,048
Net Gain (Loss) on Available-for-Sale Investments, Fair Value Option	247	(176)	2,487	(166)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, assets	31,097	23,460	31,097	23,460	28,048
Derivatives, assets	41,475	3,311	41,475	3,311	4,627
Total assets, fair value hierarchy	72,572	26,771	72,572	26,771	32,675
Derivatives, liabilities	3,426	8,324	3,426	8,324	12,330
Option Agreement	25,590		25,590
Total Liabilities	29,016		29,016
Reconciliation of fair value for Level 3 financial instruments
Balance at beginning of year			5,484	7,618
Gain (loss) from change in fair value			176	(1,226)
Issuance of option agreement			(25,590)	0
Balance at end of third quarter	(19,930)	6,392	(19,930)	6,392
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	6,805	8	6,805	8	0
Derivatives, assets	0	0	0	0	0
Total assets, fair value hierarchy	6,805	8	6,805	8	0
Derivatives, liabilities	0	0	0	0	0
Option Agreement	0		0
Total Liabilities	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	18,632	18,050	18,632	18,050	22,564
Derivatives, assets	41,475	2,321	41,475	2,321	4,627
Total assets, fair value hierarchy	60,107	20,371	60,107	20,371	27,191
Derivatives, liabilities	3,426	8,324	3,426	8,324	12,330
Option Agreement	0		0
Total Liabilities	3,426		3,426
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, assets	5,660	5,402	5,660	5,402	5,484
Derivatives, assets	0	990	0	990	0
Total assets, fair value hierarchy	5,660	6,392	5,660	6,392	5,484
Derivatives, liabilities	0	0	0	0	0
Option Agreement	25,590		25,590
Total Liabilities	$ 25,590		$ 25,590