Retirement Benefit Plans Executive Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 01, 2017	Dec. 31, 2017
Other liabilities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Deferred Compensation Arrangements, Recorded Liability		$ 259
Chief Executive Officer
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Deferred Compensation Arrangement with Individual, Base Salary	$ 1,000
Supplemental Employee Retirement Plans, Defined Benefit
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension and Other Postretirement Defined Benefit Plans, Liabilities	$ 3,101	$ 2,476