Financing Arrangments-Interest (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jul. 01, 2012	Jun. 30, 2013	Jul. 01, 2012
1% Sr. Convertible Notes due 2013 [Member]
Interest Cost Recognized For Convertible Notes
Contractual interest coupon	$ 1,162	$ 2,321	$ 3,481	$ 4,640
Amortization of bond issuance costs	318	696	1,014	1,392
Amortization of bond discount	6,964	13,276	21,022	26,301
Total interest cost recognized	8,444	16,293	25,517	32,333
1.5% Sr. Convertible Notes due 2017 [Member]
Interest Cost Recognized For Convertible Notes
Contractual interest coupon	3,750	3,750	7,500	7,500
Amortization of bond issuance costs	666	666	1,333	1,333
Amortization of bond discount	9,802	9,080	19,321	17,941
Total interest cost recognized	$ 14,218	$ 13,496	$ 28,154	$ 26,774