Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 28, 2015	Mar. 29, 2014
Cash flows from operating activities:
Net income	$ 4,754us-gaap_NetIncomeLoss	$ 5,280us-gaap_NetIncomeLoss
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	3,561	3,142
Loss on disposal of property and equipment	22	(10)
Stock-based compensation	3,107us-gaap_ShareBasedCompensation	3,078us-gaap_ShareBasedCompensation
Increase (Decrease) in Deferred Income Taxes	(102)	1,912
Tax benefit of excess stock based compensation deductions	(560)	(2,231)
Non-cash director deferred compensation	38us-gaap_OtherNoncashExpense	11us-gaap_OtherNoncashExpense
Changes in operating assets and liabilities - (use) source
Accounts receivable	33,351	2,808
Unbilled revenue	1,981	(75)
Inventory	(1,998)us-gaap_IncreaseDecreaseInInventories	4,080us-gaap_IncreaseDecreaseInInventories
Other assets	203	(3,588)
Accounts payable	(21,835)	(7,924)
Accrued expenses	(4,374)	(1,399)
Accrued compensation	(8,430)	(11,862)
Deferred revenue and customer advances	(2,080)	(665)
Long term liabilities	83	(319)
Net cash provided by operating activities	7,721	(7,762)
Cash flows from investing activities:
Additions of property and equipment	(4,445)	(2,177)
Payments for (Proceeds from) Other Investing Activities	515	0
Purchases of investments	(3,541)	(11,211)
Sales of investments	2,500	2,500
Net cash used in investing activities	(6,001)	(10,888)
Cash flows from financing activities:
Proceeds from stock option exercises	1,466	6,957
Income tax withholding payment associated with restricted stock vesting	(1,118)	(1,118)
Payments for Repurchase of Common Stock	(4,924)	0
Tax benefit of excess stock-based compensation deductions	560	2,231
Net cash provided by financing activities	(4,016)	8,070
Net increase (decrease) in cash and cash equivalents	(2,296)	(10,580)
Cash and cash equivalents, at beginning of period	185,957	165,404
Cash and cash equivalents, at end of period	183,661	154,824
Supplemental disclosure of cash flow information:
Cash paid for income taxes	1,040us-gaap_IncomeTaxesPaid	3,284us-gaap_IncomeTaxesPaid
Property, Plant and Equipment, Transfers and Changes	157	637
Noncash or Part Noncash Acquisition, Fixed Assets Acquired	$ 480	$ 1,373

Name:	us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.