Retirement Benefit Plans Defined Contribution Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 30, 2018	Dec. 31, 2017	Jan. 01, 2017
Defined Contribution Plan
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent	75.00%
Defined Contribution Plan, Employer Matching Contribution, Percent	4.00%
Defined Contribution Plan, Cost	$ 4,619	$ 4,704	$ 5,177