Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 01, 2012	Mar. 27, 2011	Dec. 25, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, assets	$ 20,202	$ 21,387	$ 19,669
Derivatives, assets	22,345	22,872	29,500
Total assets, fair value hierarchy	42,547	44,259	49,169
Derivatives, liabilities	6,054	33,599	1,908
Fair Value of Available for Sale Investments, Fair Value Option	20,190	21,359	19,657
Gain on Available for Sale Investments, Fair Value Option	1,096	157
Reconciliation of fair value measurements of the Company's warrants
Balance at beginning of year	3,724	9,155
Loss from change in fair value	795	(541)
Balance at end of period	4,519	8,614
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	12	28	12
Derivatives, assets	0	0	0
Total assets, fair value hierarchy	12	28	12
Derivatives, 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	20,190	21,359	19,657
Derivatives, assets	17,826	14,258	25,776
Total assets, fair value hierarchy	38,016	35,617	45,433
Derivatives, liabilities	6,054	33,599	1,908
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	0
Derivatives, assets	4,519	8,614	3,724
Total assets, fair value hierarchy	4,519	8,614	3,724
Derivatives, liabilities	$ 0	$ 0	$ 0