Debt (Details 1) - Convertible Senior Notes Due 2015 [Member] - Senior Notes [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 04, 2015	Jun. 28, 2014	Jul. 04, 2015	Jun. 28, 2014
Effective interest rate and components of interest expense of 2015 notes
Effective interest rate	8.10%	8.10%	8.10%	8.10%
Contractual interest expense	$ 1,178	$ 2,289	$ 2,987	$ 4,578
Amortization of debt discount	$ 2,470	$ 4,275	$ 7,500	$ 8,507