Accumulated Other Comprehensive Income (Tables)

12 Months Ended

Dec. 31, 2016

Accumulated Other Comprehensive Income [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

		Unrealized Gains
		on Available-for-Sale
(dollars in thousands)		Marketable Securities
Accumulated other comprehensive income balance as of December 27, 2014	$	4,829
Other comprehensive loss before reclassifications		(52)
Amounts reclassified from accumulated other comprehensive income		(16)
Net current period other comprehensive loss		(68)
Accumulated other comprehensive income balance as of December 26, 2015	$	4,761
Other comprehensive income before reclassifications		348
Amounts reclassified from accumulated other comprehensive income		(257)
Net current period other comprehensive income		91
Accumulated other comprehensive income balance as of December 31, 2016	$	4,852

Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]

		Gains Reclassified from
		Accumulated Other Comprehensive Income to the
		Consolidated Statements of Income
(dollars in thousands)	Location		2016		2015		2014
Unrealized gains on available-for-sale marketable securities
	Investment income	$	437	$	27	$	63
	Provision for income taxes		(180)		(11)		(26)
Total amount reclassified, net of tax		$	257	$	16	$	37