Derivatives and Fair Value of Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 29, 2014	Dec. 31, 2013
Amortized Cost
Schedule of amortized cost and estimated fair values of investments and long term debt
Short-term investments, available-for-sale	$ 334,485	$ 224,314
Short-term investments, trading debt securities	56,488	65,728
Long-term debt	91,910	92,177
Fair Value
Schedule of amortized cost and estimated fair values of investments and long term debt
Short-term investments, available-for-sale	334,818	224,076
Short-term investments, trading debt securities	57,404	66,573
Long-term debt	$ 94,341	$ 94,578