Financing Arrangements-Interest (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2015	Jun. 29, 2014	Jun. 28, 2015	Jun. 29, 2014
1.5% Sr. Convertible Notes due 2017 [Member]
Interest Cost Recognized For Convertible Notes
Contractual interest coupon	$ 3,738	$ 3,750	$ 7,476	$ 7,500
Amortization of bond issuance costs	664	666	1,329	1,333
Amortization of bond discount	11,205	10,498	22,078	20,690
Total interest cost recognized	15,607	14,914	30,883	29,523
0.5% Sr. Convertible Notes due 2020 [Member]
Interest Cost Recognized For Convertible Notes
Contractual interest coupon	1,875	1,875	3,750	3,750
Amortization of bond issuance costs	628	638	1,255	1,297
Amortization of bond discount	11,398	10,627	22,652	21,398
Total interest cost recognized	$ 13,901	$ 13,140	$ 27,657	$ 26,445