Note 6 - Fair Value of Assets and Liabilities - Carrying Value and Estimated Fair Value of Senior Notes (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 30, 2017
Euro Senior Notes, Series A [Member] | Reported Value Measurement [Member]
Senior Notes, Fair Value	$ 144,041	$ 139,623
Euro Senior Notes, Series A [Member] | Estimate of Fair Value Measurement [Member]
Senior Notes, Fair Value	142,038	138,294
Euro Senior Notes, Series B [Member] | Reported Value Measurement [Member]
Senior Notes, Fair Value	116,956	113,369
Euro Senior Notes, Series B [Member] | Estimate of Fair Value Measurement [Member]
Senior Notes, Fair Value	113,953	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	24,301	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	96,475	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	48,081
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	$ 118,303