Financing Arrangements-Interest (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2015	Sep. 28, 2014	Sep. 27, 2015	Sep. 28, 2014
1.5% Sr. Convertible Notes due 2017 [Member]
Interest Cost Recognized For Convertible Notes
Contractual interest coupon	$ 3,738	$ 3,750	$ 11,214	$ 11,250
Amortization of bond issuance costs	665	667	1,994	2,000
Amortization of bond discount	11,270	10,558	33,348	31,248
Total interest cost recognized	15,673	14,975	46,556	44,498
0.5% Sr. Convertible Notes due 2020 [Member]
Interest Cost Recognized For Convertible Notes
Contractual interest coupon	1,875	1,875	5,625	5,625
Amortization of bond issuance costs	627	627	1,882	1,924
Amortization of bond discount	11,433	10,936	34,085	32,334
Total interest cost recognized	$ 13,935	$ 13,438	$ 41,592	$ 39,883