Description of Business and Significant Accounting Policies (Narrative) (Details)	6 Months Ended
	Jun. 30, 2018
Basis Of Presentation Fiscal Year End And New Accounting Pronouncements Disclosure [Abstract]
Operating Cycle	The fiscal year of the Company consists of a 52- or 53-week period ending on the Saturday closest to December 31. Fiscal year 2018 is a 52-week period ending on December 29, 2018, with quarterly periods ending on March 31, June 30 and September 29, 2018. Fiscal year 2017 was a 52-week period ending on December 30, 2017, with quarterly periods ending on April 1, July 1 and September 30, 2017.
Year Founded	1973