Earnings Per Share (Details) - $ / shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2020	Jun. 30, 2019	Jun. 28, 2020	Jun. 30, 2019
Reconciliation of basic net earnings per share to diluted net earnings per share
Basic net earnings per share	$ 1.38	$ 2.11	$ 3.58	$ 3.52
Average shares outstanding — basic	2,632,900	2,652,500	2,633,300	2,656,700
Potential shares exercisable under stock option plans	119,600	140,800	122,600	138,600
Less: shares which could be repurchased under treasury stock method	(87,500)	(102,300)	(85,400)	(99,000)
Convertible debt shares	500	700	500	700
Average shares outstanding — diluted	2,665,500	2,691,700	2,671,000	2,697,000
Diluted net earnings per share	$ 1.36	$ 2.08	$ 3.53	$ 3.47
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	20,000		15,000