Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 28, 2015	Mar. 29, 2014
Cash Flows from Operating Activities:
Net income	$ 21,339us-gaap_NetIncomeLoss	$ 23,551us-gaap_NetIncomeLoss
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation, amortization and accretion	3,618	2,860
Provision for doubtful accounts	10us-gaap_ProvisionForDoubtfulAccounts	70us-gaap_ProvisionForDoubtfulAccounts
Benefit for deferred income taxes	(927)us-gaap_DeferredIncomeTaxExpenseBenefit	(626)us-gaap_DeferredIncomeTaxExpenseBenefit
Provision for non-cash stock compensation	340us-gaap_ShareBasedCompensation	490us-gaap_ShareBasedCompensation
Changes in assets and liabilities:
Accounts receivable	4,883	(5,380)
Inventories	(9,515)us-gaap_IncreaseDecreaseInInventories	(10,132)us-gaap_IncreaseDecreaseInInventories
Prepaids and other current assets	633	(200)
Other assets	(1,422)	(1,260)
Accounts payable	939	(3,400)
Accrued compensation and other liabilities	3,906	5,171
Cash provided by operating activities	23,804	11,144
Cash Flows from Investing Activities:
Property, plant and equipment additions	(5,749)	(7,008)
Cash used in investing activities	(5,749)	(7,008)
Cash Flows from Financing Activities:
Proceeds from exercise of stock options		262
Other stock related activity	118dorm_OtherStockRelatedActivity	199dorm_OtherStockRelatedActivity
Purchase and cancellation of common stock	(1,230)	(1,169)
Cash used in financing activities	(1,112)	(708)
Net Increase in Cash and Cash Equivalents	16,943	3,428
Cash and Cash Equivalents, Beginning of Period	47,656	60,593
Cash and Cash Equivalents, End of Period	64,599	64,021
Supplemental Cash Flow Information
Cash paid for interest expense	73us-gaap_InterestPaid	51us-gaap_InterestPaid
Cash paid for income taxes	$ 2,746us-gaap_IncomeTaxesPaidNet	$ 593us-gaap_IncomeTaxesPaidNet

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