Note 6 - Fair Value of Assets and Liabilities - Carrying Value and Estimated Fair Value of Senior Notes (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 30, 2017
Euro Senior Notes, Series A [Member] | Reported Value Measurement [Member]
Senior Notes, Fair Value	$ 135,335	$ 139,623
Euro Senior Notes, Series A [Member] | Estimate of Fair Value Measurement [Member]
Senior Notes, Fair Value	134,332	138,294
Euro Senior Notes, Series B [Member] | Reported Value Measurement [Member]
Senior Notes, Fair Value	109,887	113,369
Euro Senior Notes, Series B [Member] | Estimate of Fair Value Measurement [Member]
Senior Notes, Fair Value	107,963	111,579
US Senior Notes, Series A Due 2022 [Member] | Reported Value Measurement [Member]
Senior Notes, Fair Value	25,000	25,000
US Senior Notes, Series A Due 2022 [Member] | Estimate of Fair Value Measurement [Member]
Senior Notes, Fair Value	24,154	24,737
US Senior Notes, Series B Due 2027 [Member] | Reported Value Measurement [Member]
Senior Notes, Fair Value	100,000	100,000
US Senior Notes, Series B Due 2027 [Member] | Estimate of Fair Value Measurement [Member]
Senior Notes, Fair Value	95,711	99,992
US Senior Notes, Series A Due 2025 [Member] | Reported Value Measurement [Member]
Senior Notes, Fair Value	50,000
US Senior Notes, Series A Due 2025 [Member] | Estimate of Fair Value Measurement [Member]
Senior Notes, Fair Value	47,769
US Senior Notes, Series B Due 2030 [Member] | Reported Value Measurement [Member]
Senior Notes, Fair Value	125,000
US Senior Notes, Series B Due 2030 [Member] | Estimate of Fair Value Measurement [Member]
Senior Notes, Fair Value	$ 117,300