Note 15. Financial Instruments and Fair Value Measurements (Details) - Estimated Fair Value of Financial Instruments, Current Year (USD $) In Thousands, unless otherwise specified	Mar. 30, 2014	Dec. 29, 2013
Short-Term Investments
Available for Sale Securities	$ 48,405	$ 49,099
Commercial Paper, Not Included with Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Short-Term Investments
Available for Sale Securities	29,943	21,993
Commercial Paper, Not Included with Cash and Cash Equivalents [Member]
Short-Term Investments
Available for Sale Securities	29,943	21,993
Corporate Bond Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Short-Term Investments
Available for Sale Securities	15,864	27,106
Corporate Bond Securities [Member]
Short-Term Investments
Available for Sale Securities	15,864	27,106
Certificates of Deposit [Member] | Fair Value, Inputs, Level 1 [Member]
Short-Term Investments
Available for Sale Securities	2,598
Certificates of Deposit [Member]
Short-Term Investments
Available for Sale Securities	$ 2,598