Debt (Schedule of Debt Instruments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2017	Dec. 30, 2016
Debt Instrument [Line Items]
Total debt, including current portion	$ 232,613	$ 314,598
Series A maturing March 2018
Debt Instrument [Line Items]
Average interest rate	4.00%
Debt Instrument, Maturity Date, Description	March 2018
Total debt, including current portion	$ 0	75,000
Series B maturing March 2023
Debt Instrument [Line Items]
Average interest rate	5.01%
Debt Instrument, Maturity Date, Description	March 2023
Total debt, including current portion	$ 75,000	75,000
Series C maturing January 2020
Debt Instrument [Line Items]
Average interest rate	4.88%
Debt Instrument, Maturity Date, Description	January 2020
Total debt, including current portion	$ 75,000	75,000
Series D maturing July 2026
Debt Instrument [Line Items]
Average interest rate	5.35%
Debt Instrument, Maturity Date, Description	July 2026
Total debt, including current portion	$ 75,000	75,000
Revolving Credit Facility maturing June 2021
Debt Instrument [Line Items]
Average interest rate	2.56%
Debt Instrument, Maturity Date, Description	December 2021
Total debt, including current portion	$ 1,035	5,685
Notes payable to banks maturing 2017
Debt Instrument [Line Items]
Average interest rate	0.77%
Debt Instrument, Maturity Date, Description	2018
Total debt, including current portion	$ 6,578	$ 8,913