Earnings Per Share: (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 24, 2016	Sep. 30, 2017	Sep. 24, 2016
Earnings Per Share:
Denominator for basic EPS - weighted average common shares	4,024,692	4,116,957	4,131,269	4,113,819
Dilutive shares associated with option plans	289,720	211,211	284,916	206,465
Denominator for diluted EPS - weighted average common shares and dilutive potential common shares	4,314,412	4,328,168	4,416,185	4,320,284
Options excluded from EPS calculation - anti-dilutive (in shares)	10,753	12,868	16,057	18,348