Investments Continuous Unrealized Loss Position (Details) (USD $) In Thousands, unless otherwise specified	Mar. 29, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
In Loss Position for Less Than 12 months, Fair Value	$ 47,775	$ 71,979
In Loss Position for Less Than 12 Months, Gross Unrealized Losses	87	70
Total Fair Value	47,775	71,979
Total Gross Unrealized Losses	87	70
Securities and obligations of U.S. government agencies
Schedule of Available-for-sale Securities [Line Items]
In Loss Position for Less Than 12 months, Fair Value	47,775	71,979
In Loss Position for Less Than 12 Months, Gross Unrealized Losses	87	70
Total Fair Value	47,775	71,979
Total Gross Unrealized Losses	$ 87	$ 70