Fair Value of Financial Instruments Unobservable Inputs (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 28, 2014	Jul. 04, 2015	Jun. 28, 2014
Short-term marketable securities | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain (loss)		$ 100	$ (100)
Fair Value, Inputs, Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning fair value of Long-term marketable securities		0	5,241
Fair value of securities sold or redeemed		0	(5,488)
Realized gain from increase in fair value		0	247
Ending fair value of Long-term marketable securities	$ 0	$ 0	0
Federally-insured or FFELP guaranteed student loan auction rate securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Par value	5,700		$ 5,700
Federally-insured or FFELP guaranteed student loan auction rate securities | Fair Value, Inputs, Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of securities sold or redeemed	$ (5,200)