CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Unaudited) (USD $) In Thousands, unless otherwise specified	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Earnings [Member]	Employee Stock Notes Receivable [Member]	Noncontrolling Interest [Member]	Total
Balance at Dec. 28, 2013	$ 19,948	$ 156,129	$ 461,812	$ 3,466	$ (732)	$ 9,111	$ 649,734
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings			7,216			452	7,668
Foreign currency translation adjustment				(602)		(94)	(696)
Noncontrolling interest associated with business acquisitions						975	975
Distributions to noncontrolling interest						(701)	(701)
Issuance of shares under employee stock plans	2	97					99
Issuance of shares under stock grant programs	63	523					586
Issuance of shares under deferred compensation plans	36	(35)					1
Expense associated with share-based compensation arrangements		495					495
Accrued expense under deferred compensation plans		2,069					2,069
Payments received on employee stock notes receivable					192		192
Balance at Mar. 29, 2014	20,049	159,278	469,028	2,864	(540)	9,743	660,422
Balance at Dec. 27, 2014	19,984	162,483	502,334	1,348	(455)	13,866	699,560
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings			10,162			642	10,804
Foreign currency translation adjustment				(857)		(146)	(1,003)
Noncontrolling interest associated with business acquisitions						1,019	1,019
Distributions to noncontrolling interest						(939)	(939)
Issuance of shares under employee stock plans	12	457					469
Issuance of shares under stock grant programs	75	1,782	1				1,858
Issuance of shares under deferred compensation plans	50	(50)					0
Repurchase of shares	(1)		(76)		77		0
Tax benefits from non-qualified stock options exercised		66					66
Expense associated with share-based compensation arrangements		378					378
Accrued expense under deferred compensation plans		2,670					2,670
Payments received on employee stock notes receivable					100		100
Balance at Mar. 28, 2015	$ 20,120	$ 167,786	$ 512,421	$ 491	$ (278)	$ 14,442	$ 714,982