Micrel (MCRL) 10-K 24 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Jan. 31, 2015	Jun. 30, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	MICREL INC
Entity Central Index Key	932111
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$256
Entity Common Stock, Shares Outstanding		56,417,092

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
CURRENT ASSETS:
Cash and cash equivalents	$21,183	$23,787
Restricted cash	44	1,116
Short-term investments	65,428	64,806
Accounts receivable, less allowances: 2014, $1,058; 2013, $760	30,523	29,437
Inventories	44,136	43,201
Prepaid taxes	5,633	4,513
Prepaid expenses and other	1,612	2,698
Deferred income taxes	22,356	21,662
Total current assets	190,915	191,220
LONG-TERM INVESTMENTS	1,436	4,195
PROPERTY, PLANT AND EQUIPMENT, NET	60,453	57,779
LONG-TERM PREPAID TAXES	1,711	0
GOODWILL	8,655	8,554
INTANGIBLE ASSETS, NET	9,792	11,749
DEFERRED INCOME TAXES	2,707	1,581
OTHER ASSETS	1,511	1,046
TOTAL ASSETS	277,180	276,124
CURRENT LIABILITIES:
Accounts payable	17,376	13,502
Accrued liabilities	12,869	12,874
Deferred income on shipments to distributors	22,947	27,026
Total current liabilities	53,192	53,402
LONG-TERM INCOME TAXES PAYABLE	3,511	3,575
LONG-TERM DEFERRED INCOME TAXES	807	973
OTHER LONG-TERM LIABILITIES	162	201
Total liabilities	57,672	58,151
COMMITMENTS AND CONTINGENCIES (Note 12)
SHAREHOLDERS’ EQUITY:
Preferred stock, no par value - authorized: 5,000,000 shares; issued and outstanding: none	0	0
Common stock, no par value - authorized: 250,000,000 shares; issued and outstanding: 2014 - 56,435,555 shares; 2013 - 56,441,346 shares	0	0
Accumulated other comprehensive loss	-83	-320
Retained earnings	219,591	218,293
Total shareholders’ equity	219,508	217,973
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$277,180	$276,124

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]
Allowances for accounts receivable	$1,058	$760
Preferred stock, par value
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued
Preferred stock, shares outstanding
Common stock, par value
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	56,435,555	56,441,346
Common stock, shares outstanding	56,435,555	56,441,346

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Income Statement [Abstract]
NET REVENUES	$247,594		$237,080		$250,112
COST OF REVENUES	119,566	[1]	115,034	[1]	117,185	[1]
GROSS PROFIT	128,028		122,046		132,927
OPERATING EXPENSES:
Research and development	62,033	[1]	55,853	[1]	57,182	[1]
Selling, general and administrative	48,351	[1]	45,803	[1]	48,010	[1]
Restructuring charges	992		1,376		0
Total operating expenses	111,376		103,032		105,192
INCOME FROM OPERATIONS	16,652		19,014		27,735
INTEREST AND OTHER INCOME (EXPENSE):
Interest income	359		482		712
Other expense, net	-297		-264		-153
Total interest and other income, net	62		218		559
INCOME BEFORE INCOME TAXES AND NONCONTROLLING INTEREST	16,714		19,232		28,294
PROVISION FOR INCOME TAXES	3,167		1,584		15,966
NET INCOME	13,547		17,648		12,328
LESS: NET INCOME ATTRIBUTABLE TO NONCONTROLLING INTEREST	0				-10
NET INCOME ATTRIBUTABLE TO MICREL, INCORPORATED SHAREHOLDERS	$13,547		$17,648		$12,318
NET INCOME PER SHARE ATTRIBUTABLE TO MICREL, INCORPORATED SHAREHOLDERS:
Basic	$0.24		$0.31		$0.21
Diluted	$0.24		$0.30		$0.20
CASH DIVIDENDS DECLARED PER SHARE	$0.20		$0.14		$0.21	[2]
WEIGHTED AVERAGE SHARES USED IN COMPUTING PER SHARE AMOUNTS:
Basic	56,508		57,803		59,623
Diluted	57,538		58,506		60,288
[1]	Share-based compensation expense included in:Cost of revenues$997 $1,060 $1,178Research and development3,197 2,875 3,132Selling, general and administrative3,430 3,162 3,282
[2]	Included an accelerated cash dividend of $0.0425 per share of common stock totaling $2.5 million paid on December 27, 2012 to shareholders of record as of December 18, 2012.

Consolidated_Statements_of_Ope1

Consolidated Statements of Operations (Parenthetical) (USD $)	0 Months Ended	12 Months Ended
	Dec. 27, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accelerated cash dividend per share	$0.04
Payment of accelerated cash dividends	$2,500,000
Share-based compensation		7,624,000	7,097,000	7,592,000
Cost of revenues [Member]
Share-based compensation		997,000	1,060,000	1,178,000
Research and development [Member]
Share-based compensation		3,197,000	2,875,000	3,132,000
Selling, general and administrative [Member]
Share-based compensation		$3,430,000	$3,162,000	$3,282,000

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
NET INCOME	$13,547	$17,648	$12,328
Other comprehensive income:
Unrealized gains on investments	366	303	608
Reclassification adjustment for a realized loss on investment included in other expense	0	26	0
Income tax provision	-129	-117	-253
Other comprehensive income, net of taxes	237	212	355
COMPREHENSIVE INCOME	13,784	17,860	12,683
Less: comprehensive income attributable to noncontrolling interest	0	0	-10
COMPREHENSIVE INCOME ATTRIBUTABLE TO MICREL, INCORPORATED SHAREHOLDERS	$13,784	$17,860	$12,673

Consolidated_Statements_of_Sha

Consolidated Statements of Shareholders' Equity Statement (USD $)	Total	Common Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]
In Thousands, except Share data, unless otherwise specified
Balances, beginning at Dec. 31, 2011	$244,518	$206	($887)	$245,199	$0
Balances, beginning, shares at Dec. 31, 2011		61,038,507
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	12,328			12,318	10
Other comprehensive income, net of tax	355		355
Noncontrolling interest of PhaseLink	977	0			977
Acquisition of noncontrolling interest in PhaseLink	-932	55			-987
Share-based compensation	7,558	7,558
Payment of cash dividends	-12,072			-12,072
Repurchases of common stock, shares		-3,431,548
Repurchases of common stock	-34,551	-10,742		-23,809
Employee stock transactions, shares		599,980
Employee stock transactions	3,642	3,642
Tax effect of employee stock transactions	-185	-185
Purchases of common stock for withholding taxes on vested restricted stock, shares		-53,274
Purchases of common stock for withholding taxes on vested restricted stock	-534	-534
Balances, ending at Dec. 31, 2012	221,104	0	-532	221,636	0
Balances, ending, shares at Dec. 31, 2012		58,153,665
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17,648			17,648	0
Other comprehensive income, net of tax	212		212
Share-based compensation	7,108	7,108
Payment of cash dividends	-8,219			-8,219
Repurchases of common stock, shares		-2,405,959
Repurchases of common stock	-23,336	-10,564		-12,772
Employee stock transactions, shares		774,403
Employee stock transactions	4,390	4,390
Tax effect of employee stock transactions	-122	-122
Purchases of common stock for withholding taxes on vested restricted stock, shares		-80,763
Purchases of common stock for withholding taxes on vested restricted stock	-812	-812
Balances, ending at Dec. 31, 2013	217,973	0	-320	218,293	0
Balances, ending, shares at Dec. 31, 2013	56,441,346	56,441,346
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,547			13,547	0
Other comprehensive income, net of tax	237		237
Share-based compensation	7,644	7,644
Payment of cash dividends	-11,299			-11,299
Repurchases of common stock, shares		-1,744,095
Repurchases of common stock	-20,150	-19,200		-950
Employee stock transactions, shares		1,868,599
Employee stock transactions	13,101	13,101
Tax effect of employee stock transactions	-40	-40
Purchases of common stock for withholding taxes on vested restricted stock, shares		-130,295
Purchases of common stock for withholding taxes on vested restricted stock	-1,505	-1,505
Balances, ending at Dec. 31, 2014	$219,508	$0	($83)	$219,591	$0
Balances, ending, shares at Dec. 31, 2014	56,435,555	56,435,555

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$13,547	$17,648	$12,328
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	13,632	13,122	12,465
Share-based compensation expense	7,624	7,097	7,592
Excess tax benefits from stock-based awards	-2,046	-476	-218
Impairment of technology	0	0	1,000
(Gain) loss on disposal of assets	-21	-33	1
Deferred income tax provision	-2,115	-3,677	9,654
Other, net	0	61	0
Changes in operating assets and liabilities:
Accounts receivable	-1,086	-1,073	-1,135
Inventories	-915	208	-4,684
Prepaid taxes	-2,871	-544	2,569
Prepaid expenses and other assets	125	-1,558	-1,469
Accounts payable	1,803	-8,784	3,928
Income taxes payable	-64	683	-3,508
Accrued liabilities and other long-term liabilities	-402	2,920	-976
Deferred income on shipments to distributors	-4,079	1,258	-4,903
Net cash provided by operating activities	23,132	26,852	32,644
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of PhaseLink's net assets, net of cash acquired	0	0	-17,370
Purchase of Discera’s net assets	0	-6,122	0
Purchases of property, plant and equipment	-11,734	-7,325	-9,022
Purchase of intangible asset	0	-410	0
Purchases of investments	-55,166	-59,653	-55,819
Proceeds from sale and maturities of investments	57,669	71,490	60,108
Change in restricted cash	1,072	-825	-291
Net cash used in investing activities	-8,159	-2,845	-22,394
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of debt	0	0	-282
Proceeds from the issuance of common stock	13,101	4,390	3,642
Repurchases of common stock	-19,970	-23,336	-34,551
Payment of cash dividends	-11,299	-8,219	-12,072
Purchase of stock for withholding taxes on vested restricted stock	-1,455	-812	-534
Excess tax benefits from stock-based awards	2,046	476	218
Net cash used in financing activities	-17,577	-27,501	-43,579
NET DECREASE IN CASH AND CASH EQUIVALENTS	-2,604	-3,494	-33,329
CASH AND CASH EQUIVALENTS - Beginning of year	23,787	27,281	60,610
CASH AND CASH EQUIVALENTS - End of year	21,183	23,787	27,281
Cash paid during the year for:
Interest	0	0	2
Income taxes	$8,432	$5,457	$7,060

Significant_Accounting_Policie

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
NATURE OF BUSINESS	Nature of Business — Micrel, Incorporated and its wholly-owned subsidiaries (collectively, the “Company”) develops, manufactures and markets analog, mixed-signal and digital semiconductor devices. The Company also provides custom and foundry services which include silicon wafer fabrication, integrated circuit (“IC”) assembly and testing. The Company’s products are sold principally in North America, Asia, and Europe for use in a variety of products, including those in the mobility, enterprise/cloud infrastructure, wireline communications and industrial and automotive markets. The Company’s wafer foundry services are provided to a wide range of customers that produce electronic systems for communications, consumer, automotive and military applications. The Company produces the majority of its wafers at the Company’s wafer fabrication facilities located in San Jose, California. After wafer fabrication, the completed wafers are then separated into individual circuits and packaged at independent assembly and final test contract facilities primarily located in Malaysia, Thailand, Taiwan and China.
SIGNIFICANT ACCOUNTING POLICIES	Basis of Presentation — The accompanying consolidated financial data has been prepared by the Company pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) and is presented in conformity with U.S. generally accepted accounting principles (“US GAAP”).
	Principles of Consolidation — The accompanying consolidated financial statements include the accounts of Micrel, Incorporated and its wholly-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated.
	Use of Estimates — In accordance with US GAAP, management utilizes certain estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. On an on-going basis, management evaluates its estimates and judgments. Management bases its estimates and judgments on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. The primary estimates underlying the Company’s financial statements include allowances for doubtful accounts receivable, allowances for product returns and price adjustments, provisions for obsolete and slow moving inventory, share-based compensation, income taxes, litigation losses, valuation of auction-rate securities and accruals for other liabilities. Actual results could differ from those estimates.
	Cash Equivalents — The Company considers all highly liquid investments with remaining maturities of three months or less at the time of purchase to be cash equivalents.
	Investments — Investments purchased with remaining maturity of greater than three months and less than 12 months are classified as short-term. Investments purchased with remaining maturity dates of 12 months or greater are classified either as short-term or as long-term based on maturities and the Company’s intent with regard to those securities (expectations of sales and redemptions). Short-term investments at December 31, 2014, consisted primarily of liquid municipal securities, corporate debt securities, commercial paper and U.S. government agencies securities and were classified as available-for-sale securities. Long-term investments at December 31, 2014, consisted of auction-rate notes secured by student loans and were classified as available-for-sale securities. Available-for sale securities are stated at market value with unrealized gains and losses included in accumulated other comprehensive loss, a component of shareholders’ equity. At December 31, 2014, accumulated other comprehensive loss of $0.1 million consisted of unrealized gains and losses on investments. Unrealized losses are charged against income when a decline in the fair market value of an individual security is determined to be other than temporary. Realized gains and losses on investments are included in other income or expense.
	Certain Significant Risks and Uncertainties — Financial instruments that potentially subject the Company to concentrations of credit risk consist of cash and cash equivalents, investments and accounts receivable. Risks associated with cash are mitigated by banking with creditworthy institutions. Cash equivalents and investments consist primarily of commercial paper, money market funds, corporate debt securities, municipal securities and auction-rate notes and are regularly monitored by management. Credit risk with respect to the trade receivables is spread over geographically diverse customers. The Company performs ongoing credit evaluations of its customers and maintains an allowance for potential credit losses. At December 31, 2014, distributors A, C and B accounted for 24%, 15%, and 13%, respectively, of total accounts receivable.  At December 31, 2013, distributors A and B accounted for 36%, and 11%, respectively, of total accounts receivable.
	Micrel currently purchases certain components from a limited group of vendors. The packaging of the Company’s products is performed by, and certain of the raw materials included in such products are obtained from, a limited group of suppliers. The wafer supply for the Company’s LAN products is currently dependent upon two large third-party wafer foundry suppliers. Although the Company seeks to reduce its dependence on limited source suppliers, disruption or termination of any of these sources could occur and such disruptions could have an adverse effect on the Company’s financial condition, results of operations, or cash flows.
	The Company participates in a dynamic high technology industry and believes that changes in any of the following areas could have a material adverse effect on the Company’s future financial position, results of operations, or cash flows: changes in the overall demand for products offered by the Company; competitive pressures in the form of new products or price reductions on current products; advances and trends in new technologies and industry standards; changes in product mix; changes in third-party manufacturers; changes in key suppliers; changes in certain strategic relationships or customer relationships; litigation or claims against the Company based on intellectual property, patents, product, regulatory or other factors; risks associated with the ability to obtain necessary components; risks associated with the Company’s ability to attract and retain employees necessary to support its growth.
	Inventories — Inventories are stated at the lower of cost (first-in, first-out method) or market. The Company records adjustments to write down the cost of obsolete and excess inventory to the estimated market value based on historical and forecasted demand for its products. Once an inventory write-down provision is established, it is maintained until the product to which it relates is sold or otherwise disposed of.
	Property, Plant and Equipment — Property, plant and equipment are stated at cost, net of accumulated depreciation and amortization. Depreciation and amortization are computed using the straight-line method over the estimated useful lives of the assets.
	Goodwill — Goodwill represents the excess of the purchase price over the fair value of net tangible and identifiable intangible assets acquired. Goodwill is measured and tested for impairment annually at the reporting unit level during the last quarter of the Company's fiscal year, or more frequently if the Company believes indicators of impairment exist. Events that could trigger a more frequent impairment review may include adverse industry or economic trends, restructuring actions, lower projections of profitability, or a sustained decline in our market capitalization. The Company has allocated its goodwill to its timing and communications reporting unit.
	Qualitative factors are assessed to determine whether it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If the qualitative assessment indicates that the carrying amount is more likely than not higher than the fair value, goodwill is tested for impairment based on a two-step test. The first step requires comparing the fair value of our reporting unit to its net book value, including goodwill. Determining the fair value of a reporting unit is judgmental in nature and involves the use of significant estimates and assumptions. These estimates and assumptions include projected revenues and forecasted operating margins used to calculate projected future cash flows, risk-adjusted discount rates, future economic and market conditions and determination of appropriate market comparables. The Company bases its fair value estimates on assumptions it believes to be reasonable. Actual future results may differ from those estimates. Future competitive, market and economic conditions could negatively impact key assumptions including our market capitalization or the carrying value of the Company’s net assets which could require it to realize an impairment of its goodwill.
	A potential impairment exists if the fair value of the reporting unit is less than its net book value. The second step of the process is only performed if a potential impairment exists, and it involves determining the difference between the fair value of the reporting unit’s net assets other than goodwill to the fair value of the reporting unit and if the difference is less than the net book value of goodwill, an impairment exists and is recorded. No goodwill impairment was recognized in 2014, 2013 and 2012.
	Impairment of Long-Lived Assets — The Company reviews its purchased intangible assets with finite lives for impairment whenever events or changes in circumstances indicate the carrying value of an asset may not be recoverable. Recoverability of these intangible assets is assessed based on the estimated undiscounted future cash flows expected to result from the use of the asset. If the undiscounted future cash flows are less than the carrying amount, the purchased intangible assets with finite lives are considered to be impaired. The amount of the impairment is measured as the difference between the carrying amount of these assets and the fair value.
	The Company’s business combinations have included the purchase of in-process research and development assets that are not amortizable until the underlying project is complete. The Company assesses that its in-process research and development project is complete when all material research and development costs have been incurred and no significant risks remain. The Company reviews the carrying value of indefinite-lived intangible assets for impairment at least annually during the last quarter of its fiscal year, or more frequently if it believes indicators of impairment exist.
	In 2012, the Company recorded an impairment of $1.0 million as a component of research and development expense for a developed technology which was replaced by more advanced technologies. In 2014 and 2013, no indicators of impairment were identified.
	Revenue Recognition and Receivables — The Company generates revenue by selling products to original equipment manufacturers (“OEM”), sell-through distributors and sell-in distributors. The Company’s policy is to recognize revenue from sales to customers when the rights and risks of ownership have passed to the customer, when persuasive evidence of an arrangement exists, the product has been delivered, the price is fixed or determinable and collection of the resulting receivable is reasonably assured.
	The Company provides certain sell-through distributors price protection rights and pricing adjustments subsequent to the initial product shipment to allow them to price the Company's products competitively for specific resale opportunities.  As these price adjustments have historically been significant, and price adjustments are difficult to reliably estimate, the Company defers recognition of revenue and related cost of revenues (in the balance sheet line item “deferred income on shipments to distributors”) derived from sales to these distributors until they have resold the Company’s products to their customers. Although revenue and related cost of revenues are not recognized, the Company records an accounts receivable and relieves inventory at the time of initial product shipment.  The Company's standard terms are EXW or FCA shipping point, payment terms are enforced from shipment date and legal title and risk of inventory loss passes to the sell-through distributor upon shipment. In addition, the Company estimates and records an adjustment for sell-through distributor price adjustments for which the specific resale transaction has been completed but the price adjustment claim has not yet been received by the Company.
	During the third quarter of 2014, the Company amended the terms of its agreements with certain sell-through distributors. These amendments included the removal of significant return rights, price protection and pricing adjustments subsequent to the initial product shipment. Therefore, upon amendment of the agreements, these distributors were changed from sell-through distributors to sell-in distributors and the Company recognized the revenue for sales to these distributors upon the initial product shipments to these distributors, net of estimated allowance for returns established based upon historical return rates. In addition, revenue was recognized for unsold inventory held by these distributors on the date of change. The effect of changing these sell-through distributors to sell-in distributors resulted in a one-time increase in revenue of approximately $5.1 million and related cost of revenues of $1.6 million related to unsold inventory held by these distributors at June 30, 2014.
	Sales to OEM customers and sell-in distributors are recognized based upon the shipment terms of the sale transaction when all other revenue recognition criteria have been met.  The Company does not grant return rights, price protection or pricing adjustments to OEM customers. The Company offers limited contractual stock rotation rights to sell-in distributors. At the time of shipment to sell-in distributors, an allowance for returns is established based upon historical return rates, and an allowance for price adjustments is established based on an estimate of price adjustments to be granted. Actual future returns and price adjustments could be different than the allowance established.
	The Company’s accounts receivable balances represent trade accounts receivables which have been recorded at invoiced amount and do not bear interest.  The Company maintains an allowance for doubtful accounts for estimated uncollectible accounts receivable. This estimate is based on an analysis of specific customer creditworthiness and historical bad debt experience.
	Shipping and Handling Costs — Shipping and handling costs are included in sales and marketing expense and are recognized as period expenses as incurred.
	Litigation — An estimated liability is accrued when it is determined to be probable that a liability has been incurred and the amount of loss can be reasonably estimated. The liability accrual is charged to income in the period such determination is made. Legal fees are expensed as incurred. The Company regularly evaluates current information available to determine whether such accruals should be made.
	Research and Development Expenses — Research and development costs are expensed as incurred and consist primarily of payroll and other headcount related costs and cost of materials associated with the development of new wafer fabrication processes and the definition, design and development of semiconductor products. The Company also expenses prototype wafers and new production mask sets related to new products as research and development costs until products based on new designs are released to production.
	Self Insurance — The Company utilizes third-party insurance carriers subject to varying retention levels of self insurance. The Company is self-insured for a portion of the losses and liabilities primarily associated with earthquake damage, workers’ compensation claims and health benefit claims. Losses are accrued based upon the Company’s estimates of the aggregate liability for claims incurred using historical experience.
	Advertising Expenses — The Company expenses advertising costs to selling, general and administrative expense as incurred. Advertising expenses for 2014, 2013 and 2012 were $0.3 million, $0.1 million and $1.0 million, respectively.
	Income Taxes — Deferred tax assets and liabilities are recognized for the expected future tax consequences of events that have been reflected in the financial statements. Deferred tax assets and liabilities are determined based on the differences between the book and tax bases of assets and liabilities and operating loss carryforwards, using tax rates expected to be in effect for the years in which the differences are expected to reverse. A valuation allowance is provided to reduce net deferred tax assets if, based upon the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained based on the technical merits of the position. The tax benefit of any tax position that meets the more-likely-than-not recognition threshold is calculated at the largest amount that is more than 50% likely of being realized upon resolution of the uncertainty. To the extent a full benefit is not expected to be realized on the uncertain tax position, a reduction to a deferred asset is recorded or an income tax liability is established. Interest and penalties on income tax obligations, including uncertain tax positions, are included in the income tax provision.
	Share-based Compensation — Share-based compensation is measured at the grant date based on the fair value of the award and is recognized over the employee's requisite service period as expense in the consolidated statements of operations. Share-based compensation costs for stock option grants are based on the fair value calculated from a stock option pricing model on the date of grant. The Company has utilized the Black-Scholes option pricing model to determine the fair value for stock option grants.  The fair value of stock option grants is recognized as compensation expense on a straight-line basis over the vesting period of the grants. Compensation expense recognized is shown in the operating activities section of the consolidated statements of cash flows. Cash flows resulting from the tax benefits from tax deductions in excess of the compensation cost recognized (excess tax benefits) is shown in the financing activities section of the consolidated statements of cash flows.
	Net Income Per Common and Diluted Share — Basic net income per share is computed by dividing net income attributable to Micrel, Incorporated shareholders by the number of weighted-average common shares outstanding. Diluted net income per share reflects potential dilution from outstanding stock options and restricted stock units (“RSUs”) using the treasury stock method. Reconciliation of weighted-average shares used in computing basic and diluted net income per share attributable to Micrel, Incorporated shareholders is as follows (in thousands):
		Years Ended December 31,
		2014	2013	2012
	Shares used in computing basic net income per share	56,508	57,803	59,623
	Dilutive effect of stock options and restricted stock units	1,030	703	665
	Shares used in computing diluted net income per share	57,538	58,506	60,288
	For the years ended December 31, 2014, 2013 and 2012, 2.7 million, 5.4 million and 5.2 million shares underlying stock options and restricted stock units, respectively, have been excluded from the weighted-average number of common shares outstanding for the diluted net income per share computations as they were anti-dilutive.
	Fair Value of Financial Instruments — Financial instruments included in the Company’s consolidated balance sheets at December 31, 2014 and 2013, consist of cash, cash equivalents, accounts receivable, accounts payable and investments. For cash, the carrying amount is the fair value. The carrying amount for cash equivalents, accounts receivable and accounts payable approximates fair value because of the short maturity of those instruments. The fair values of investments are based on quoted market prices, quoted prices for similar assets or valuation models for investments for which quoted market prices are unavailable.

Recently_Issued_Accounting_Sta

Recently Issued Accounting Standards	12 Months Ended
	Dec. 31, 2014
New Accounting Pronouncements [Abstract]
New Accounting Pronouncements and Changes in Accounting Principles [Text Block]	RECENTLY ISSUED ACCOUNTING STANDARDS
	In April 2014, the Financial Accounting Standards Board (“FASB”) issued an accounting standards update to change the requirements for reporting discontinued operations. This guidance modifies the definition of discontinued operations by limiting discontinued operations reporting to disposals of components of an entity that represent strategic shifts that have (or will have) a major effect on an entity's operations and financial results. The guidance requires expanded disclosures for discontinued operations for the assets, liabilities, revenues, and expenses of discontinued operations, and also requires an entity to disclose the pretax profit or loss of an individually significant component of an entity that does not qualify for discontinued operations reporting. The Company is required to adopt this standard for its interim and annual periods beginning after December 15, 2014. In the event that a future disposition meets the revised criteria, the Company expects that this standard will have an impact on the presentation of the Company's financial statements and the Company will present the appropriate disclosures at that time.
	In May 2014, the FASB issued an accounting standards update on the recognition of revenue from contracts with customers. The guidance modifies the financial reporting of revenue. The core principle of the guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The guidance requires enhanced disclosures for the nature, amount, timing, and uncertainty of revenue that is recognized. The Company is required to adopt this standard for its interim and annual periods beginning after December 15, 2016. Early adoption is not permitted. The guidance may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The Company is currently evaluating the impact of adopting this guidance on its consolidated financial statements.
	In June 2014, the FASB issued an accounting standards update on the accounting for share-based payments when the terms of an award provide that a performance target could be achieved after the requisite service period. The guidance requires that a performance target that affects vesting and that could be achieved after the requisite service period be treated as a performance condition. The Company is required to adopt this standard for its interim and annual periods beginning after December 15, 2015. Early adoption is permitted. The guidance may be applied on a prospective or retrospective basis. The adoption of this standard is not expected to have a material impact on the Company's consolidated financial statements.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
ACQUISITIONS	ACQUISITIONS
	Discera, Inc.
	On August 30, 2013, the Company signed a definitive agreement to acquire specific net assets of Discera, Inc. (“Discera”), a private company based in San Jose, California, which qualifies as an acquisition of a business for financial accounting purposes. The acquisition closed on September 9, 2013. The total cash consideration was approximately $7.2 million, plus $1.1 million of assumed liabilities. Of the $7.2 million, $6.1 million was paid upon closing, and $1.1 million was withheld to secure the indemnification obligations from the closing date through September 9, 2014, which was included in restricted cash on the consolidated balance sheet at December 31, 2013. The Company paid $1.0 million of the restricted cash in the second half of 2014. The objective of the acquisition is to complement and expand Micrel’s high performance clock and timing product portfolio, as well as expand its MEMS (micro-electrical mechanical systems) capabilities. The addition of the Discera MEMS product line will also enhance Micrel’s MEMS presence, intellectual property and capability. The Company has included the financial results of Discera in its consolidated financial statements beginning on the acquisition date. Pro forma financial disclosures are not presented herein as the financial results of this acquisition are considered immaterial.
	During the first quarter of 2014, goodwill recorded from the Discera transaction was increased by approximately $0.1 million to $2.6 million and the purchase price allocation was completed.
	Identifiable intangible assets
	Fair values for the acquired developed technology, customer relationships, trademarks and non-competition agreements and in-process research and development (“IPR&D”) were determined based on various methods including excess earnings method, relief from royalty method and with-or-without method. The values of the developed technology and customer relationships are amortized over an estimated useful life of ten and three years, respectively. The non-competition agreements are amortized over one year. The values of trademarks are amortized over ten years.
	The fair value of the acquired IPR&D was determined through estimates and valuation techniques applied to the projected cash flows of the acquired research projects. As it was determined that the underlying projects had not reached technological feasibility at the date of acquisition, the amounts allocated to IPR&D will not be amortized to expense until completion of the related projects. Upon the completion of development for each project, the acquired IPR&D will be amortized over its useful life. The Company expects to complete these projects and begin to amortize the related IPR&D assets in 2015.
	PhaseLink Company Limited
	On April 2, 2012, the Company acquired a controlling interest in PhaseLink™ Company Limited (“PhaseLink”), a private company based in Taiwan and in San Jose, California. The Company acquired approximately 95% of the outstanding shares of PhaseLink for $19.7 million in cash ($16.4 million net of cash acquired). On December 20, 2012, the Company acquired the remaining 5% noncontrolling interest in cash ($0.9 million) that resulted in 100% ownership in PhaseLink. The objective of the acquisition is to complement Micrel’s high performance clock generation products, add distribution products for the communications market and to expand its product offerings into the consumer and industrial markets. In addition, the Company expects the acquisition to enhance its technology portfolio and further expand its research and development capabilities. The Company has included the financial results of PhaseLink in its consolidated financial statements beginning on the acquisition date of April 2, 2012. Pro forma financial disclosures are not presented herein as the financial results of this acquisition are considered immaterial.
	Identifiable intangible assets
	Fair values for the acquired developed technology, customer relationships, trademarks and non-competition agreements and IPR&D were determined based on various methods including excess earnings method, relief from royalty method and with-or-without method. The values of the developed technology and customer relationships are amortized over an estimated useful life of 10 years. The non-competition agreements are amortized over a two-year period. The values of trademarks are amortized over two to five years.
	The fair value of the acquired IPR&D was determined through estimates and valuation techniques based on the terms and details of the acquisition. As it was determined that the underlying projects had not reached technological feasibility at the date of acquisition, the amounts allocated to IPR&D will not be expensed until completion of the related projects. Upon the completion of development for each project, the acquired IPR&D will be amortized over its useful life. The Company expects to complete these projects and begin to amortize the related IPR&D assets in 2015.

Investments

Investments	12 Months Ended
	Dec. 31, 2014
Investments [Abstract]
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure	INVESTMENTS
	A summary of the Company’s short-term investments at December 31, 2014 and 2013 was as follows (in thousands):
		31-Dec-14										31-Dec-13
		Cost			Gross Unrealized		Gross Unrealized			Fair		Cost		Gross Unrealized		Gross Unrealized			Fair
					Gains		Losses			Value				Gains		Losses			Value
	Corporate Debt Securities	$	43,327		$	3	$	(68	)	$	43,262	$	36,947	$	10	$	—		$	36,957
	Commercial Paper	14,975			5		(3		)	14,977		13,991		2		—			13,993
	Municipal Securities	5,191			3		—			5,194		13,858		—		(2		)	13,856
	U.S. Government Agencies Securities	2,000			—		(5		)	1,995		—		—		—			—
	Total	$	65,493		$	11	$	(76	)	$	65,428	$	64,796	$	12	$	(2	)	$	64,806
	At December 31, 2014, the Company had no short-term investments that have been in a significant continuous unrealized loss position for more than twelve months.
	A summary of the Company’s long-term investments at December 31, 2014 and December 31, 2013 was as follows (in thousands):
		31-Dec-14										31-Dec-13
		Cost			Gross Unrealized		Gross Unrealized			Fair		Cost		Gross Unrealized		Gross Unrealized			Fair
					Gains		Losses			Value				Gains		Losses			Value
	Auction Rate Notes	$	1,500		$	—	$	(64	)	$	1,436	$	4,700	$	—	$	(505	)	$	4,195
	During the year ended December 31, 2014, the Company sold $3.2 million of auction-rate notes at par value. At December 31, 2014, the Company had remaining $1.5 million principal value of auction-rate notes, the fair value of which has been measured using Level 3 inputs. Auction-rate notes are securities that are structured with short-term interest rate reset dates of generally less than ninety days, but with contractual maturities that can be in excess of ten years. At the end of each reset period, which occurs every seven or twenty eight days for the securities held by the Company, investors can sell or continue to hold the securities at par. As a result of sell orders exceeding buy orders, auctions for the student loan-backed notes held by the Company have failed at December 31, 2014. To date, the Company has collected all interest receivable on all of its auction-rate notes when due and expects to continue to do so in the future. The principal associated with failed auctions will not be accessible until a successful auction occurs, a buyer is found outside of the auction process, the issuers redeem the securities, or the issuers repay principal over time from cash flows prior to final maturity or final payments come due according to a contractual maturity of 33 years. The Company has classified all auction-rate notes as long-term investments at December 31, 2014 and 2013. In the event of a failed auction, the notes bear interest at a predetermined maximum rate based on the credit rating of notes as determined by one or more nationally recognized statistical rating organizations. For the auction-rate notes held by the Company at December 31, 2014, the maximum interest rate is generally one month LIBOR plus 1.5% based on the notes’ rating as of that date.
	To determine the fair value of financial instruments, the Company uses a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (level 1 measurement) and the lowest priority to unobservable inputs (level 3 measurement). The three levels of the fair value hierarchy are described below:
	•	Level 1 - Quoted prices in active markets for identical assets or liabilities.
	•	Level 2 - Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
	•	Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
	A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The Company's short-term investments are classified within Level 2 of the fair value hierarchy because they are valued using quoted market prices for similar securities, broker or dealer quotations, or other observable inputs.
	The types of instruments valued based on quoted market prices in active markets include money market funds. Such instruments are generally classified within Level 1 of the fair value hierarchy. The types of instruments valued based on other observable inputs include commercial paper, corporate debt securities, municipal securities and U.S. government agencies securities. Such instruments are generally classified within Level 2 of the fair value hierarchy. The types of instruments valued based on unobservable inputs consist of the auction-rate notes held by the Company. Such instruments are generally classified within Level 3 of the fair value hierarchy. The Company estimated the fair value of these auction-rate notes using a combination of observable transactions for similar securities and a discounted cash flow model incorporating assumptions that market participants would use in their estimates of fair value. Some of these assumptions include estimates for interest rates, timing and amount of cash flows and expected holding periods of the auction-rate notes. Based on this assessment of fair value, at December 31, 2014, the Company determined there was a cumulative decline in the fair value of its auction-rate notes and recorded less than $0.1 million ($0.1 million pre-tax) temporary impairment of these securities to accumulated other comprehensive loss, a component of shareholders’ equity.
	Financial assets and liabilities measured at fair value on a recurring basis were as follows (in thousands):
		31-Dec-14
		Quoted Prices in			Significant Other		Significant			Total
		Active Markets			Observable Inputs		Unobservable
		for Identical			Level 2		Inputs
		Assets					Level 3
		Level 1
	Money Market Funds (1)	$	4,725		$	—	$	—		$	4,725
	Corporate Debt Securities (2)	—			43,262		—			43,262
	Commercial Paper (2)	—			14,977		—			14,977
	Municipal Securities (2)	—			5,194		—			5,194
	U.S. Government Agencies Securities (2)	—			1,995		—			1,995
	Auction-rate notes (3)	—			—		1,436			1,436
	Total	$	4,725		$	65,428	$	1,436		$	71,589
		31-Dec-13
		Quoted Prices in			Significant Other		Significant			Total
		Active Markets			Observable Inputs		Unobservable
		for Identical			Level 2		Inputs
		Assets					Level 3
		Level 1
	Money Market Funds (1)	$	16,945		$	—	$	—		$	16,945
	Corporate Debt Securities (2)	—			36,957		—			36,957
	Commercial Paper (2)	—			13,993		—			13,993
	Municipal Securities (2)	—			13,856		—			13,856
	Auction-rate notes (3)	—			—		4,195			4,195
	Total	$	16,945		$	64,806	$	4,195		$	85,946
	__________
	(1) Included in cash and cash equivalents
	(2) Included in short-term investments
	(3) Included in long-term investments
	There were no significant transfers between Level 1 and Level 2 of the fair value hierarchy.
	For the year ended December 31, 2014, the changes in the Company’s Level 3 securities (consisting of auction-rate notes) were as follows (in thousands):
		Fair Value
		Measurements
		Using Significant
		Unobservable
		Inputs
		(Level 3)
	Beginning balance, December 31, 2013	$	4,195
	Transfers in and/or out of Level 3	—
	Total unrealized gains, before tax, included in other comprehensive income	441
Sales	(3,200		)
Ending balance, December 31, 2014	$	1,436

Inventories

Inventories	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
INVENTORIES	INVENTORIES
	Inventories consisted of the following (in thousands):
		December 31,		December 31,
		2014		2013
	Finished goods	$	15,395	$	11,592
	Work in process	27,500		30,109
	Raw materials	1,241		1,500
	Total inventories	$	44,136	$	43,201

Property_Plant_and_Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	PROPERTY, PLANT AND EQUIPMENT
	Property, plant and equipment consisted of the following (in thousands):
		Life	December 31,			December 31,
			2014			2013
	Machinery and equipment	5 years	$	189,335		$	180,851
	Land	—	8,101			8,101
	Buildings and improvements	*	54,483			53,915
	Computer equipment and software	3 years	11,094			11,742
	Office furniture and fixtures	5 years	1,528			1,928
			264,541			256,537
	Accumulated depreciation		(204,088		)	(198,758		)
	Total property, plant and equipment, net		$	60,453		$	57,779
	__________
	* Buildings are depreciated over 10 years to 30 years. Leasehold improvements are depreciated over the shorter of the useful life or respective lease terms.
	Depreciation expense for the years ended December 31, 2014, 2013 and 2012 was $11.0 million, $11.1 million and $11.5 million, respectively.
	The Company had received unpaid property, plant and equipment purchases, excluding asset retirement obligations, of $3.0 million and $1.0 million at December 31, 2014 and 2013, respectively.

Intangible_Assets_Intangible_A

Intangible Assets Intangible Assets	12 Months Ended
	Dec. 31, 2014
Finite-Lived Intangible Assets, Net [Abstract]
INTANGIBLE ASSETS	INTANGIBLE ASSETS
	Intangible Assets
	The following table sets forth the components of intangible assets as follows (in thousands):
			December 31, 2014							December 31, 2013
			Gross		Accumulated			Net		Gross		Accumulated			Net
			Carrying		Amortization			Carrying		Carrying		Amortization			Carrying
			Amount					Amount		Amount					Amount
	Developed and core technology		$	7,443	$	(1,810	)	$	5,633	$	7,783	$	(986	)	$	6,797
	Customer relationships		3,800		(1,181		)	2,619		3,800		(552		)	3,248
	Trademarks		610		(370		)	240		610		(284		)	326
	Non-competition agreements		—		—			—		450		(372		)	78
	In-process research and development		1,300		—			1,300		1,300		—			1,300
			$	13,153	$	(3,361	)	$	9,792	$	13,943	$	(2,194	)	$	11,749
	The above intangible assets acquired in connection with the Discera acquisition in 2013 of $2.7 million, PhaseLink acquisition in 2012 of $8.3 million, and other acquired intangible assets of $2.1 million are amortized over their estimated useful lives ranging from one to ten years using the straight-line method. Total intangible amortization expense for the years ended December 31, 2014, 2013 and 2012 was $1.6 million, $1.4 million and $0.8 million, respectively.
	The estimated future amortization expense of intangible assets at December 31, 2014 was as follows (in thousands):
	Year Ending December 31,
	2015	$	1,535
	2016	1,510
	2017	1,281
	2018	1,223
	2019	1,140
	Thereafter	3,103
		$	9,792
	During 2012, the Company recorded an impairment of $1.0 million as a component of research and development expense for purchased technology which was replaced by more advanced technologies.

Borrowing_Arrangements

Borrowing Arrangements	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
BORROWING ARRANGEMENTS	BORROWING ARRANGEMENTS
	Under the terms of an unsecured credit facility with Bank of the West that expires on April 30, 2015, the Company has a $5.0 million line of credit available for general working capital needs, which includes a $5.0 million letter of credit sub-facility including a $2.0 million foreign exchange sub-facility. Interest rates under the facility are based on one of three interest rates, at the Company’s option: (1) a variable alternate base rate plus 1.0%, the alternate base rate being the greater of (x) Bank of the West’s prime rate, (y) the Fed Funds Rate plus 0.5% or (z) daily adjusted one-month LIBOR plus 1.0%; (2) floating one-month LIBOR plus 2.0% or (3) fixed LIBOR for one, two, three or six month periods, plus 2.0%. The agreement includes certain restrictive covenants and, at December 31, 2014, the Company was in compliance with such covenants. At December 31, 2014, the Company had no borrowings under the line of credit facility.
	The Company's borrowing arrangements include a provision for the issuance of commercial or standby letters of credit by the bank on behalf of the Company. The letters of credit are issued to guarantee payments for the Company’s workers compensation program. At December 31, 2014, there was $0.3 million in letters of credit outstanding.
	Through the PhaseLink acquisition, the Company acquired two term loans totaling $0.3 million with a local bank in Taiwan. The Company paid off the acquired bank loans in full in June 2012.

Shareholders_Equity_and_ShareB

Shareholders' Equity and Share-Based Compensation	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
SHAREHOLDERS' EQUITY AND SHARE-BASED COMPENSATION	SHAREHOLDERS' EQUITY AND SHARE-BASED COMPENSATION
	Preferred Stock
	The Company has authorized 5.0 million shares of preferred stock, no par value, of which none were issued or outstanding at December 31, 2014. The preferred stock may be issued from time to time in one or more series. The Board of Directors is authorized to determine or alter the rights, preferences, privileges and restrictions of such preferred stock.
	Share Repurchase Program
	Since February 2010, the Company's Board of Directors has authorized the repurchase of $145.0 million of the Company's common stock. Shares of common stock purchased pursuant to the repurchase program are cancelled from outstanding shares upon repurchase and credited to an authorized and unissued reserve account. Share repurchases are recorded as a reduction to common stock to the extent available. Any amounts repurchased which are in excess of the existing total common stock balance are recorded as a reduction of retained earnings. Share repurchases are intended to reduce the number of outstanding shares of common stock to increase shareholder value and offset dilution from the Company’s share-based compensation plans and the Micrel, Incorporated Employee Stock Purchase Plan (“ESPP”). During the year ended December 31, 2014, the Company repurchased 1.7 million shares of its common stock for an aggregate price of $20.2 million, which included $0.2 million of share repurchases pending cash settlement at December 31, 2014. The total available for repurchase, at December 31, 2014, was $30.7 million.
	Incentive Award Plans
	The Company has in effect incentive stock plans under which incentive stock options have been granted to employees and restricted stock units and non-qualified stock options have been granted to employees and non-employee members of the Board of Directors.
	On May 24, 2012, the Company’s shareholders approved the Micrel, Incorporated 2012 Equity Incentive Award Plan (the “2012 Plan”) and the reservation of an aggregate of 6.0 million shares of common stock for issuance pursuant to the 2012 Plan.
	The 2012 Plan has replaced in its entirety the Company’s 1994 Stock Option Plan, the Micrel, Incorporated 2000 Non-Qualified Stock Incentive Plan and the Micrel, Incorporated 2003 Incentive Award Plan (the “Prior Plans”). No new award has been made under these plans since May 24, 2012. However, the shares of common stock that remained available for issuance under the Prior Plans were added to the shares reserved for issuance under the 2012 Plan. In addition, shares of common stock subject to awards already granted under the Micrel, Incorporated 2003 Incentive Award Plan that terminate, expire or lapse will become available for issuance under the 2012 Plan, provided that the aggregate number of shares of common stock available for issuance under the 2012 Plan is reduced by two (2) shares for each share of common stock delivered in settlement of any award other than a stock option or stock appreciation right. On the effective date of the 2012 Plan which was May 24, 2012, the Prior Plans were terminated, provided, that any awards outstanding under the Prior Plans remain outstanding pursuant to their respective terms. At December 31, 2014, there were 3.4 million shares available for future grants under the Company’s 2012 Plan.
	Stock Options
	Options granted under the 2012 Plan typically become exercisable in cumulative annual increments of either 20% or 25% per year from the date of grant. The term of each stock option is no more than ten years from the date of grant.
	Option activity under the Company’s incentive stock plans is as follows:
			Number			Weighted Avg.
			of Shares			Exercise Price
						Per Share
	Outstanding, December 31, 2011 (3,366,610 shares exercisable at a weighted average price of $10.31 per share and a weighted average remaining contractual life of 4.3 years)		7,960,170			$	10.26
	Granted		1,494,250			10.13
	Exercised		(415,156	)		7.91
	Canceled		(882,995	)		11.22
	Outstanding, December 31, 2012 (4,068,071 shares exercisable at a weighted average price of $9.98 per share and a weighted average remaining contractual life of 4.2 years)		8,156,269			10.25
	Granted		700,300			9.96
	Exercised		(522,218	)		7.62
	Canceled		(821,263	)		10.92
	Outstanding, December 31, 2013 (4,286,232 shares exercisable at a weighted average price of $10.12 per share and a weighted average remaining contractual life of 4.3 years)		7,513,088			10.34
	Granted		445,767			10.85
	Exercised		(1,485,784	)		8.56
	Canceled		(586,132	)		12.38
	Outstanding, December 31, 2014 (3,512,257 shares exercisable at a weighted average price of $10.53 per share and a weighted average remaining contractual life of 4.8 years)		5,886,939			$	10.64
	At December 31, 2014, the estimated number of options expected to vest and exercisable was 5.2 million shares with a weighted average remaining contractual life of 5.7 years and an estimated aggregate intrinsic value of $20.3 million.
	The weighted average fair value (computed using the Black-Scholes option pricing model) of options granted under the stock option plans during the years ended December 31, 2014, 2013 and 2012 was $2.93, $2.86 and $2.96 per share, respectively.  The total intrinsic value of options (which is the amount by which the stock price exceeded the exercise price of the options on the date of exercise) exercised during the years ended December 31, 2014, 2013 and 2012 was $4.2 million, $1.2 million and $1.0 million, respectively. During the years ended December 31, 2014, 2013 and 2012, the amount of cash received from the exercise of stock options was $12.7 million, $4.0 million and $3.3 million, respectively. The excess tax benefit realized from the exercise of non-qualified stock options and disqualifying dispositions of incentive stock options was $2.0 million, $0.5 million and $0.2 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	Additional information regarding options outstanding at December 31, 2014 was as follows:
			Stock Options Outstanding									Options Exercisable
	Range of Exercise Prices		Number Outstanding			Weighted Avg. Remaining Contractual Life (yrs)		Weighted Avg. Exercise Price Per Share				Number Exercisable	Weighted Avg. Exercise Price Per Share
	$ 4.72 to $ 7.00		132,020			3.5		$	6.63			132,020	$	6.63
	$ 7.01 to $ 7.46		298,340			4.1		7.25				293,380	7.25
	$ 7.49 to $ 8.00		288,283			4.4		7.82				283,803	7.82
	$ 8.01 to $ 9.00		151,588			3.6		8.54				141,785	8.53
	$ 9.01 to $10.00		1,282,671			6.5		9.61				643,954	9.65
	$10.01 to $11.00		1,982,999			6.8		10.41				868,161	10.4
	$11.01 to $13.00		697,258			6		12.09				407,874	12.16
	$13.01 to $16.00		973,780			5.5		13.7				661,280	13.67
	$16.01 to $49.50		80,000			1.2		16.21				80,000	16.21
			5,886,939			5.9		$	10.64			3,512,257	$	10.53
	At December 31, 2014, the aggregate pre-tax intrinsic value (which was the amount by which the $14.51 closing price of the Company’s common stock at December 31, 2014 exceeded the exercise price of the in the money options) of options outstanding and options exercisable was approximately $22.9 million and $14.1 million, respectively.
	The fair value of the stock options granted under the Company’s option plans was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:
		Years Ended December 31,
		2014			2013			2012
	Expected term (years)	6			5.9			5.8
	Stock volatility	30.7	%		34.5	%		36.6	%
	Risk free interest rates	2	%		1.6	%		1	%
	Dividends during expected terms	1.6	%		1.9	%		1.6	%
	Expected term is based on an analysis of historical exercises and the remaining contractual life of options.
	Stock volatility is based upon historical stock price volatility.
	Risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant.
	Dividend yield is based on annualized dividends per share and the Company’s average stock price.
	The Company estimates potential forfeitures of stock grants and accordingly adjusts compensation cost recorded. The estimate of forfeitures will be adjusted over the requisite service period to the extent that actual forfeitures differ, or are expected to differ, from such estimates. Changes in estimated forfeitures will be recognized through a cumulative catch-up adjustment in the period of change and will also impact the amount of share-based compensation to be recognized in future periods.
	Restricted Stock Units
	The 2012 Plan and 2003 Plan also provide for the use of incentive awards other than stock options.  In October 2007, the Company’s Compensation Committee approved a plan to begin granting restricted stock units (“RSUs”) to employees in accordance with the provisions of the 2003 Plan.  At December 31, 2014, approximately 83% of the RSUs would vest in four equal installments annually over four years. Approximately 14% of the RSUs would vest one third on each of the third, fourth and fifth annual anniversaries of the grant date.  Information with respect to outstanding RSU activity is as follows:
						Weighted
			Number			Average
			of Shares			Grant-Date
						Fair Value
	Outstanding, December 31, 2011		667,277			$	9.73
	Granted		417,531			9.67
Vested		(146,327	)		9.49
Forfeited		(61,431	)		9.65
Outstanding, December 31, 2012		877,050			9.83
Granted		591,974			9.31
Vested		(209,819	)		9.6
Forfeited		(63,943	)		9.69
Outstanding, December 31, 2013		1,195,262			9.63
Granted		780,225			10.78
Vested		(349,451	)		9.61
Forfeited		(116,935	)		9.89
Outstanding, December 31, 2014		1,509,101			$	10.21
At December 31, 2014, the estimated number of RSUs expected to vest was 1.3 million shares with a weighted average remaining contractual life of 2.7 years and an estimated aggregate intrinsic value of $19.2 million. The aggregate intrinsic value of vested RSUs amount to $4.0 million for the year ended December 31, 2014.
Share-based Compensation
The following table shows total share-based compensation expense recognized in the Consolidated Statements of Operations for the years ended December 31, 2014, 2013 and 2012 (in thousands):
	Years Ended December 31,
	2014				2013				2012
Cost of revenues	$	997			$	1,060			$	1,178
Research and development	3,197				2,875				3,132
Selling, general and administrative	3,430				3,162				3,282
Pre-tax share-based compensation expense	7,624				7,097				7,592
Less income tax effect	(2,613		)		(2,314		)		(2,583		)
Net share-based compensation expense	$	5,011			$	4,783			$	5,009
Total share-based compensation capitalized as part of inventory at both December 31, 2014 and 2013 was $0.2 million, respectively. At December 31, 2014, there was $4.8 million of total unrecognized share-based compensation related to non-vested stock option awards and $10.8 million related to restricted stock units which are expected to be recognized over a weighted-average period of 2.44 years and 2.89 years, respectively.
Employee Stock Purchase Plan
Under the Company’s Employee Stock Purchase Plan (“ESPP”), eligible employees are permitted to have salary withholdings to purchase shares of common stock at a price equal to 95% of the market value of the stock at the end of each three-month offer period, subject to an annual limitation. The ESPP is considered non-compensatory per current share-based compensation accounting guidelines. The aggregate number of shares of common stock which may be issued under the plan shall be no more than 2.0 million shares. Shares of common stock issued under the ESPP during 2014, 2013 and 2012 were less than 0.1 million in each of the years at a weighted average price of $11.43, $9.32 and $9.40 respectively.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES
	The income tax provision for the years ended December 31, 2014, 2013 and 2012, as a percentage of income before income taxes, was 19%, 8% and 56%, respectively.
	A reconciliation of the statutory federal income tax rate to the effective tax rate for the years ended December 31 was as follows:
			2014			2013			2012
	Statutory federal income tax rate		35	%		35	%		35	%
	Research and development credit		(14	)		(22	)		—
	Qualified production activities deduction		(5	)		(3	)		(4	)
	State income taxes (net of federal income tax benefit)		—			—			(2	)
	Non-deductible stock compensation		—			1			1
	Valuation allowance		—			—			27
	Deemed dividend income		—			3			—
	Other *		3			(6	)		(1	)
	Effective tax rate		19	%		8	%		56	%
	* Other, in 2014 and 2013, includes foreign tax rate differential, foreign tax credits and other expenditures not deductible for tax purposes which are all individually insignificant.
	The provision for income taxes for the years ended December 31, 2014, 2013, and 2012 consisted of the following (in thousands):
			2014				2013				2012
	Current:
	Federal		$	4,869			$	4,833			$	8,847
	State		78				(66		)		(1,731		)
	Foreign		544				494				563
	Total current		5,491				5,261				7,679
	Deferred:
	Federal		(2,179		)		(3,698		)		(8,489		)
	State		(5		)		(31		)		16,901
	Foreign		(140		)		52				(125		)
	Total deferred		(2,324		)		(3,677		)		8,287
	Total provision		$	3,167			$	1,584			$	15,966
	Pre-tax income from U.S. and non-U.S. jurisdictions was $16.6 million and less than $0.1 million, respectively, for the year ended December 31, 2014. Pre-tax income from U.S. and non-U.S. jurisdictions was $16.9 million and $2.3 million, respectively, for the year ended December 31, 2013. Pre-tax income from U.S. and non-U.S. jurisdictions was $28.0 million and $0.3 million, respectively, for the year ended December 31, 2012.
	Deferred tax assets and liabilities result primarily from temporary differences between book and tax bases of assets and liabilities and state research and development credit carryforwards. The Company had net deferred tax assets of $24.3 million at December 31, 2014. The Company must regularly assess the likelihood that future taxable income levels will be sufficient to ultimately realize the tax benefits of these deferred tax assets. The Company believes that future taxable income levels will be sufficient to realize the tax benefits of net deferred tax assets. Therefore, the Company has not established a valuation allowance except for a valuation allowance of $12.2 million and $9.0 million, respectively, that was established against state deferred assets at December 31, 2014 and 2013 due to California tax law changes in 2012 which require mandatory single sales factor apportionment in California for most multi-state taxpayers for tax years beginning on or after January 1, 2013. Should the Company determine that future realization of these tax benefits is not more likely than not, additional valuation allowances would be established which would increase the Company’s tax provision in the period of such determination.
	Deferred tax assets and liabilities at December 31, 2014 and 2013 were as follows (in thousands):
			2014				2013
	Deferred tax assets:
	Accruals, reserves and other amounts not currently deductible		$	13,034			$	11,346
	Deferred income		8,106				9,547
	Tax credit carryforwards		12,184				9,170
	Non-qualified share-based compensation		6,245				6,115
	Capitalized research and development		18				—
	Unrealized loss on investments and other		181				278
	Gross deferred tax assets		39,768				36,456
	Valuation allowance		(12,229		)		(8,999		)
	Total deferred tax assets		27,539				27,457
	Deferred tax liabilities:
	Long-lived assets		(3,265		)		(5,187		)
	Foreign undistributed earnings		(18		)		—
	Total deferred tax liability		(3,283		)		(5,187		)
	Net deferred tax assets (current and non-current)		$	24,256			$	22,270
	Included in net deferred tax assets are credit carryforwards. The Company has available state research and development credit carryforwards of approximately $22.1 million. The state research credit carryforwards are not subject to expiration and may be carried forward indefinitely until utilized.
	At December 31, 2014, the gross liability for uncertain tax positions was $7.6 million and the net liability, reduced for the federal effects of potential state tax exposures, was $6.0 million. If these uncertain tax positions are sustained upon tax authority audit, or otherwise become certain, a net $3.5 million would favorably affect the Company’s tax provision in such future periods. The remaining $2.5 million would increase deferred assets on which a valuation allowance is placed and would be expected to also increase the valuation allowance by a corresponding amount. The $3.5 million liability is included in long-term income taxes payable. The Company does not anticipate a significant change to unrecognized tax benefits for uncertain income tax positions within the next 12 months.
	The amount of unrecognized tax benefits for the years ended December 31 consisted of the following (in thousands):
		2014				2013				2012
	Beginning balance	$	9,433			$	8,259			$	8,532
	Additions based on tax positions related to the current year	909				762				487
	Additions for tax positions related to prior years	662				1,593				77
	Subtractions for tax positions related to prior years and settlements of audits	(4,959		)		(1,181		)		(837		)
	Ending balance	$	6,045			$	9,433			$	8,259
	The unrecognized tax benefits presented above include amounts related to potential tax exposures, which are presented net of federal tax benefits.
	During 2014, the Company recognized $4.9 million of previously unrecognized tax benefits due to expiration of statutes of limitations and settlement of the California FTB audit.
	The Company continues to recognize interest and penalties related to uncertain tax benefits as part of the income tax provision. At December 31, 2014 and 2013, the Company had $0.3 million and $0.3 million, respectively, accrued for interest and none accrued for penalties for both years. These accruals were included as a component of long-term income taxes payable for $3.5 million and reduction of prepaid taxes of less than $0.1 million at December 31, 2014.
	The Company is required to file U.S. federal income tax returns as well as income tax returns in various states and foreign jurisdictions. The Company may be subject to examination by the Internal Revenue Service (“IRS”) for calendar years 2010 and forward. Significant state tax jurisdictions include California and Texas, and generally, the Company is subject to routine examination for years 2008 and forward in these jurisdictions. In addition, any research and development credit carryforwards that were generated in prior years and utilized in these years may also be subject to examination by respective state taxing authorities. Generally, the Company is subject to routine examination for years 2007 and forward in various immaterial foreign tax jurisdictions in which it operates.

Accrued_Liabilities

Accrued Liabilities	12 Months Ended
	Dec. 31, 2014
Accrued Liabilities [Abstract]
Accrued Liabilities	ACCRUED LIABILITIES
	Accrued liabilities consisted of the following (in thousands):
		December 31,		December 31,
		2014		2013
	Accrued compensation	$	7,050	$	5,767
	Accrued commissions	1,605		1,666
	Accrued restructuring	360		902
	Other accrued liabilities	3,854		4,539
	Total accrued liabilities	$	12,869	$	12,874

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES
	Lease Agreements
	The Company leases some of its facilities and equipment under operating lease agreements that expire in the years 2015 through 2019. Rent expense is recognized on a straight-line basis over the term of the lease.
	Future minimum payments under these agreements are as follows (in thousands):
	Year Ending December 31,
	2015	$	960
	2016	526
	2017	420
	2018	120
	2019	21
	Total	$	2,047
	Rent expense under operating leases for each of the years ended December 31, 2014, 2013 and 2012 was $1.1 million.
	Open Purchase Orders
	At December 31, 2014, the Company had approximately $19.4 million in open purchase orders. Open purchase orders are defined as agreements to purchase goods or services that are enforceable and legally binding and that specify all significant terms, including: fixed or minimum quantities to be purchased; fixed, minimum or variable pricing provisions; and the approximate timing of the transactions. These obligations primarily relate to future purchases of wafer fabrication raw materials, foundry wafers, assembly and testing services and manufacturing equipment. The amounts are based on the Company’s contractual commitments.
	Letters of Credit
	Micrel’s borrowing arrangements include a provision for the issuance of commercial or standby letters of credit by the bank on behalf of the Company. At December 31, 2014, there was $0.3 million in letters of credit outstanding. The letters of credit are issued to guarantee payments for the Company’s workers compensation program.
	Indemnification Obligations
	Micrel is a party to a variety of contractual relationships pursuant under which it may be obligated to indemnify the other party with respect to certain matters. Typically, these obligations arise in the context of contracts entered into by Micrel, for regular sales and purchasing activities, under which Micrel may agree to hold the other party harmless against losses arising from claims related to such matters as title to assets sold, certain intellectual property rights, specified environmental matters, certain income taxes, etc.  In these circumstances, indemnification by Micrel is customarily conditioned on the other party making a claim pursuant to the procedures specified in the particular contract or in Micrel’s standard terms and conditions, which procedures may allow Micrel to challenge the other party’s claims, or afford Micrel the right to settle such claims in its sole discretion.  Further, Micrel’s obligations under these agreements may be limited in terms of time and/or amount, and in some instances, Micrel may have recourse against third parties for certain payments made by it under these agreements.
	It is not possible to predict the maximum potential amount of future payments or indemnification costs under these or similar agreements due to the conditional nature of Micrel’s obligations and the unique facts and circumstances involved in each particular agreement. Historically, payments made by Micrel under these agreements have not had a material effect on its business, financial condition, cash flows, or results of operations.
	Legal Matters
	On November 1, 2008, Nadatel Co., Ltd. (“Nadatel”), a video surveillance equipment supplier based in Seoul Korea, filed a complaint against the Company for product liability and tort-based damages with the Seoul Central District Court in Seoul, Korea. In 2006 and 2007, Nadatel purchased approximately 17,000 of the Company’s low-dropout voltage regulators for use in its closed circuit television digital video recorder application for security systems. Nadatel claimed that the parts failed in the field, resulting in malfunction of its application, recall of the application and replacement of circuit boards incorporating the Company’s part. The Company settled this claim in June 2012 pursuant to a court-mediated agreement without admitting to liability or product defects. Despite the Company’s assessment that the claims asserted by Nadatel are untrue, it settled this protracted litigation in order to avoid further legal expense and distraction. The settlement amount of approximately $0.2 million was recorded in June 2012 as a component of selling, general and administrative expenses for the year ended December 31, 2012.
	Additional claims may arise against the Company in its normal course of business. Generally, litigation is subject to inherent uncertainties, and the Company can provide no assurance that it will prevail in any particular lawsuit. Accordingly, litigation could result in substantial costs and diversion of resources and could have a material adverse effect on the Company’s financial condition, results of operations or cash flows. At December 31, 2014, the Company has not recorded any accrual for contingent liabilities associated with legal proceedings on the assessment that liabilities are not probable. Further, ranges of possible losses in these matters cannot be reasonably estimated at this time.

ProfitSharing_401k_Plan

Profit-Sharing 401(k) Plan	12 Months Ended
	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
PROFIT SHARING 401(K) PLAN	PROFIT-SHARING 401(k) PLAN
	The Company has a profit-sharing and deferred compensation plan (the “Plan”). All employees completing one month of service are eligible to participate in the Plan. Participants may contribute 1% to 15% of their annual compensation on a before tax basis, subject to Internal Revenue Service limitations. Profit-sharing contributions by the Company are determined at the discretion of the Board of Directors. The Company accrued $0.4 million in contributions for the year ended December 31, 2014 and made $0.2 million and $0.4 million in contributions to the Plan for the years ended December 31, 2013 and 2012, respectively. Participants vest in the Company’s contributions ratably over six years of service.

Segment_Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
SEGMENT REPORTING	SEGMENT REPORTING
	The Company currently operates in one segment: the design, manufacturing, marketing and sale of semiconductor products.
	For the year ended December 31, 2014, no OEM customer accounted for more than 10% of the Company’s net revenues and distributors A and B accounted for 25% and 18% of the Company’s net revenues, respectively. For the year ended December 31, 2013, no OEM customer accounted for more than 10% of the Company’s net revenues and distributors A and B accounted for 29% and 17% of the Company’s net revenues, respectively. For the year ended December 31, 2012, one OEM customer accounted for 10% of the Company’s net revenues and distributors A and B accounted for 22% and 15% of the Company’s net revenues, respectively. The increase in percentage of revenue from our largest distributor from 2012 to 2013 was primarily due to its acquisition and integration of one of our other significant distributors in 2013.
	The Company recorded revenue from customers located throughout the United States; Canada and Mexico (collectively referred to as “Other North American Countries”); the United Kingdom, Italy, Germany, France, Israel, Sweden, Hungary, Austria, Finland, Switzerland, and other European countries (collectively referred to as “Europe”); Korea; Taiwan; Singapore; China; Japan; Hong Kong; and Malaysia and other Asian countries (collectively referred to as “Other Asian Countries”). Revenues by major geographic area are based on the geographic location of the OEMs or the distributors who have purchased the Company’s products. The geographic locations of the Company’s distributors may be different from the geographic locations of the end customers.
	Geographic Information (in thousands):
		Years Ended December 31,
		2014				2013				2012
		Total Net		Long-Lived		Total Net		Long-Lived		Total Net		Long-Lived
		Revenues		Assets (1)		Revenues		Assets(1)		Revenues		Assets (1)
	United States of America	$	55,574	$	50,125	$	62,667	$	48,432	$	66,267	$	51,715
	Other North American Countries	176		—		144		—		193		—
	Korea	23,324		9		28,050		16		36,896		24
	Taiwan	25,114		3,093		23,503		2,956		22,507		3,492
	Singapore	31,899		9		26,353		9		23,899		8
	China	16,073		1,684		15,873		2,424		16,183		1,417
	Hong Kong	43,060		60		33,881		86		37,300		215
	Japan	16,582		2		14,686		23		14,329		1
	Other Asian Countries	1,377		5,447		1,259		3,727		1,284		3,717
	Europe	34,415		24		30,664		106		31,254		103
	Total	$	247,594	$	60,453	$	237,080	$	57,779	$	250,112	$	60,692
	__________
	(1) Long-lived assets consist of property, plant and equipment.

Dividends

Dividends	12 Months Ended
	Dec. 31, 2014
Dividends, Common Stock [Abstract]
DIVIDENDS	DIVIDENDS
	During the years ended December 31, 2014, 2013 and 2012, the Company paid cash dividends of $11.3 million, $8.2 million and $12.1 million, respectively, representing $0.20, $0.1425 and $0.205 per common share, respectively.
	Cash dividends per common share for the year ended December 31, 2012 included an accelerated cash dividend of $0.0425 per share of common stock totaling $2.5 million paid on December 27, 2012 to shareholders of record at December 18, 2012. The accelerated dividend was in lieu of the quarterly dividend that the Company would have otherwise announced with its quarterly financial results for the fourth quarter of 2012, and that would have been paid in the first quarter of 2013.

Restructuring

Restructuring	12 Months Ended
	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Activities Disclosure	RESTRUCTURING CHARGES
	In 2014, the Company continued its efforts to reduce operating expenses. Therefore, the Company recorded restructuring charges of $1.0 million related to workforce reductions and facility closure. The Company paid $1.5 million related to severance costs in the year ended December 31, 2014 and expects to pay the remaining amount accrued in 2015, which is included in accrued liabilities on the consolidated balance sheet. In 2013, the Company recorded restructuring charges of $1.4 million related to workforce reductions. The following table summarizes the activity related to the accrual for restructuring charges for the year ended December 31, 2014 and 2013 by event (in thousands):
		Plan Initiated in Q4'13			Plan Initiated in Q3'14			Plan Initiated in Q4'14			Total
	Restructuring charges	$	1,376								$	1,376
	Payments	(474		)							(474		)
	Balance at December 31, 2013	902									902
	Restructuring charges	—			631			361			992
	Payments	(882		)	(560		)	(92		)	(1,534		)
	Balance at December 31, 2014	$	20		$	71		$	269		$	360

Subsequent_Event_Notes

Subsequent Event (Notes)	12 Months Ended
	Dec. 31, 2014
Subsequent Event [Line Items]
Subsequent Events [Text Block]	SUBSEQUENT EVENT
	On January 29, 2015, the Company’s Board of Directors declared a cash dividend of $0.05 per share of common stock, payable on February 25, 2015 to shareholders of record as of February 11, 2015.

Supplemental_Quarterly_Financi

Supplemental Quarterly Financial Summary - Unaudited Supplemental Quarterly Financial Summary - Unaudited	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information [Text Block]	SUPPLEMENTAL QUARTERLY FINANCIAL SUMMARY — UNAUDITED
	(in thousands, except per share amounts)	Three Months Ended 2014
		March 31,		June 30,		Sept. 30,		Dec. 31,
	Net revenues	$	59,857	$	62,339	$	67,480	$	57,918
	Gross profit	$	31,219	$	32,791	$	34,408	$	29,610
	Net income (1)	$	2,289	$	3,529	$	4,675	$	3,054
	Net income per share:
	Basic (1)	$	0.04	$	0.06	$	0.08	$	0.05
	Diluted (1)	$	0.04	$	0.06	$	0.08	$	0.05
	Weighted-average shares used in computing
	per share amounts:
	Basic	56,388		56,537		56,642		56,490
	Diluted	57,208		57,448		57,708		57,710
	Cash dividends per common share	$	0.05	$	0.05	$	0.05	$	0.05
	(in thousands, except per share amounts)	Three Months Ended 2013
		March 31,		June 30,		Sept. 30,		Dec. 31,
	Net revenues	$	59,733	$	59,171	$	58,169	$	60,007
	Gross profit	$	31,080	$	31,082	$	29,471	$	30,413
	Net income (2)	$	5,245	$	5,035	$	4,004	$	3,364
	Net income:
	Basic (2)	$	0.09	$	0.09	$	0.07	$	0.06
	Diluted (2)	$	0.09	$	0.09	$	0.07	$	0.06
	Weighted-average shares used in computing
	per share amounts:
	Basic	58,270		58,303		57,752		56,908
	Diluted	59,030		59,007		58,440		57,546
	Cash dividends per common share	$	—	$	0.0425	$	0.05	$	0.05
	__________
	(1) During the third and fourth quarter of 2014, the Company recorded a restructuring charge of $0.5 million and $0.5 million for employee severances and facility closure, respectively.
	(2) During the fourth quarter of 2013, the Company recorded a restructuring charge of $1.4 million for employee severances.

Valuations_and_Qualifying_Acco

Valuations and Qualifying Accounts	12 Months Ended
	Dec. 31, 2014
Valuation and Qualifying Accounts [Abstract]
VALUATION AND QUALIFYING ACCOUNTS	MICREL, INCORPORATED
	VALUATION AND QUALIFYING ACCOUNTS
	For the Years Ended December 31, 2014, 2013, and 2012
	(In thousands)
	Description	Balance at Beginning		Allowance Additions or			Returns and Price
		of Year		(Reductions)			Adjustments			Bad Debt			Balance at
										Write-offs			End of Year
	Year Ended December 31, 2014
	Allowances for OEM and sell-in distributor returns and price adjustments	$	737	$	1,970		$	(1,889	)	$	—		$	818
	Allowances for unclaimed sell-through distributor price adjustments (1)	—		64,530			(64,397		)	—			133
	Allowances for doubtful accounts	23		114			—			(30		)	107
	Total allowances	$	760	$	66,614		$	(66,286	)	$	(30	)	$	1,058
	Year Ended December 31, 2013
	Allowances for OEM and sell-in distributor returns and price adjustments	$	712	$	1,954		$	(1,929	)	$	—		$	737
	Allowances for unclaimed sell-through distributor price adjustments (1)	51		77,129			(77,180		)	—			—
	Allowances for doubtful accounts	49		(26		)	—			—			23
	Total allowances	$	812	$	79,057		$	(79,109	)	$	—		$	760
	Year Ended December 31, 2012
	Allowances for OEM and sell-in distributor returns and price adjustments	$	1,066	$	1,452		$	(1,806	)	$	—		$	712
	Allowances for unclaimed sell-through distributor price adjustments (1)	169		73,674			(73,792		)	—			51
	Allowances for doubtful accounts	59		(10		)	—			—			49
	Total allowances	$	1,294	$	75,116		$	(75,598	)	$	—		$	812
	___________
	(1) The Company estimates and records an allowance for sell-through distributor price adjustments for which the specific resale transaction has been completed, but the price adjustment claim has not yet been received from the sell-through distributor. This allowance typically represents approximately one to three weeks of unclaimed price adjustments.

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Basis of Accounting, Policy	The accompanying consolidated financial data has been prepared by the Company pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) and is presented in conformity with U.S. generally accepted accounting principles (“US GAAP”).
Consolidation, Policy	The accompanying consolidated financial statements include the accounts of Micrel, Incorporated and its wholly-owned subsidiaries. All significant intercompany accounts and transactions have been eliminated.
Use of Estimates, Policy	In accordance with US GAAP, management utilizes certain estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. On an on-going basis, management evaluates its estimates and judgments. Management bases its estimates and judgments on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. The primary estimates underlying the Company’s financial statements include allowances for doubtful accounts receivable, allowances for product returns and price adjustments, provisions for obsolete and slow moving inventory, share-based compensation, income taxes, litigation losses, valuation of auction-rate securities and accruals for other liabilities. Actual results could differ from those estimates.
Cash and Cash Equivalents, Policy	The Company considers all highly liquid investments with remaining maturities of three months or less at the time of purchase to be cash equivalents.
Investment, Policy	Investments purchased with remaining maturity of greater than three months and less than 12 months are classified as short-term. Investments purchased with remaining maturity dates of 12 months or greater are classified either as short-term or as long-term based on maturities and the Company’s intent with regard to those securities (expectations of sales and redemptions). Short-term investments at December 31, 2014, consisted primarily of liquid municipal securities, corporate debt securities, commercial paper and U.S. government agencies securities and were classified as available-for-sale securities. Long-term investments at December 31, 2014, consisted of auction-rate notes secured by student loans and were classified as available-for-sale securities. Available-for sale securities are stated at market value with unrealized gains and losses included in accumulated other comprehensive loss, a component of shareholders’ equity. At December 31, 2014, accumulated other comprehensive loss of $0.1 million consisted of unrealized gains and losses on investments. Unrealized losses are charged against income when a decline in the fair market value of an individual security is determined to be other than temporary. Realized gains and losses on investments are included in other income or expense.
Concentration of Risk, Policy	Financial instruments that potentially subject the Company to concentrations of credit risk consist of cash and cash equivalents, investments and accounts receivable. Risks associated with cash are mitigated by banking with creditworthy institutions. Cash equivalents and investments consist primarily of commercial paper, money market funds, corporate debt securities, municipal securities and auction-rate notes and are regularly monitored by management. Credit risk with respect to the trade receivables is spread over geographically diverse customers. The Company performs ongoing credit evaluations of its customers and maintains an allowance for potential credit losses. At December 31, 2014, distributors A, C and B accounted for 24%, 15%, and 13%, respectively, of total accounts receivable.  At December 31, 2013, distributors A and B accounted for 36%, and 11%, respectively, of total accounts receivable.
	Micrel currently purchases certain components from a limited group of vendors. The packaging of the Company’s products is performed by, and certain of the raw materials included in such products are obtained from, a limited group of suppliers. The wafer supply for the Company’s LAN products is currently dependent upon two large third-party wafer foundry suppliers. Although the Company seeks to reduce its dependence on limited source suppliers, disruption or termination of any of these sources could occur and such disruptions could have an adverse effect on the Company’s financial condition, results of operations, or cash flows.
	The Company participates in a dynamic high technology industry and believes that changes in any of the following areas could have a material adverse effect on the Company’s future financial position, results of operations, or cash flows: changes in the overall demand for products offered by the Company; competitive pressures in the form of new products or price reductions on current products; advances and trends in new technologies and industry standards; changes in product mix; changes in third-party manufacturers; changes in key suppliers; changes in certain strategic relationships or customer relationships; litigation or claims against the Company based on intellectual property, patents, product, regulatory or other factors; risks associated with the ability to obtain necessary components; risks associated with the Company’s ability to attract and retain employees necessary to support its growth.
Inventory, Policy	Inventories are stated at the lower of cost (first-in, first-out method) or market. The Company records adjustments to write down the cost of obsolete and excess inventory to the estimated market value based on historical and forecasted demand for its products. Once an inventory write-down provision is established, it is maintained until the product to which it relates is sold or otherwise disposed of.
Property, Plant and Equipment, Policy	Property, plant and equipment are stated at cost, net of accumulated depreciation and amortization. Depreciation and amortization are computed using the straight-line method over the estimated useful lives of the assets.
Goodwill, Policy	Goodwill represents the excess of the purchase price over the fair value of net tangible and identifiable intangible assets acquired. Goodwill is measured and tested for impairment annually at the reporting unit level during the last quarter of the Company's fiscal year, or more frequently if the Company believes indicators of impairment exist. Events that could trigger a more frequent impairment review may include adverse industry or economic trends, restructuring actions, lower projections of profitability, or a sustained decline in our market capitalization. The Company has allocated its goodwill to its timing and communications reporting unit.
	Qualitative factors are assessed to determine whether it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If the qualitative assessment indicates that the carrying amount is more likely than not higher than the fair value, goodwill is tested for impairment based on a two-step test. The first step requires comparing the fair value of our reporting unit to its net book value, including goodwill. Determining the fair value of a reporting unit is judgmental in nature and involves the use of significant estimates and assumptions. These estimates and assumptions include projected revenues and forecasted operating margins used to calculate projected future cash flows, risk-adjusted discount rates, future economic and market conditions and determination of appropriate market comparables. The Company bases its fair value estimates on assumptions it believes to be reasonable. Actual future results may differ from those estimates. Future competitive, market and economic conditions could negatively impact key assumptions including our market capitalization or the carrying value of the Company’s net assets which could require it to realize an impairment of its goodwill.
	A potential impairment exists if the fair value of the reporting unit is less than its net book value. The second step of the process is only performed if a potential impairment exists, and it involves determining the difference between the fair value of the reporting unit’s net assets other than goodwill to the fair value of the reporting unit and if the difference is less than the net book value of goodwill, an impairment exists and is recorded. No goodwill impairment was recognized in 2014, 2013 and 2012.
Impairment of Long-Lived Assets, Policy	The Company reviews its purchased intangible assets with finite lives for impairment whenever events or changes in circumstances indicate the carrying value of an asset may not be recoverable. Recoverability of these intangible assets is assessed based on the estimated undiscounted future cash flows expected to result from the use of the asset. If the undiscounted future cash flows are less than the carrying amount, the purchased intangible assets with finite lives are considered to be impaired. The amount of the impairment is measured as the difference between the carrying amount of these assets and the fair value.
	The Company’s business combinations have included the purchase of in-process research and development assets that are not amortizable until the underlying project is complete. The Company assesses that its in-process research and development project is complete when all material research and development costs have been incurred and no significant risks remain. The Company reviews the carrying value of indefinite-lived intangible assets for impairment at least annually during the last quarter of its fiscal year, or more frequently if it believes indicators of impairment exist.
	In 2012, the Company recorded an impairment of $1.0 million as a component of research and development expense for a developed technology which was replaced by more advanced technologies. In 2014 and 2013, no indicators of impairment were identified.
Revenue Recognition, Policy	The Company generates revenue by selling products to original equipment manufacturers (“OEM”), sell-through distributors and sell-in distributors. The Company’s policy is to recognize revenue from sales to customers when the rights and risks of ownership have passed to the customer, when persuasive evidence of an arrangement exists, the product has been delivered, the price is fixed or determinable and collection of the resulting receivable is reasonably assured.
	The Company provides certain sell-through distributors price protection rights and pricing adjustments subsequent to the initial product shipment to allow them to price the Company's products competitively for specific resale opportunities.  As these price adjustments have historically been significant, and price adjustments are difficult to reliably estimate, the Company defers recognition of revenue and related cost of revenues (in the balance sheet line item “deferred income on shipments to distributors”) derived from sales to these distributors until they have resold the Company’s products to their customers. Although revenue and related cost of revenues are not recognized, the Company records an accounts receivable and relieves inventory at the time of initial product shipment.  The Company's standard terms are EXW or FCA shipping point, payment terms are enforced from shipment date and legal title and risk of inventory loss passes to the sell-through distributor upon shipment. In addition, the Company estimates and records an adjustment for sell-through distributor price adjustments for which the specific resale transaction has been completed but the price adjustment claim has not yet been received by the Company.
	During the third quarter of 2014, the Company amended the terms of its agreements with certain sell-through distributors. These amendments included the removal of significant return rights, price protection and pricing adjustments subsequent to the initial product shipment. Therefore, upon amendment of the agreements, these distributors were changed from sell-through distributors to sell-in distributors and the Company recognized the revenue for sales to these distributors upon the initial product shipments to these distributors, net of estimated allowance for returns established based upon historical return rates. In addition, revenue was recognized for unsold inventory held by these distributors on the date of change. The effect of changing these sell-through distributors to sell-in distributors resulted in a one-time increase in revenue of approximately $5.1 million and related cost of revenues of $1.6 million related to unsold inventory held by these distributors at June 30, 2014.
	Sales to OEM customers and sell-in distributors are recognized based upon the shipment terms of the sale transaction when all other revenue recognition criteria have been met.  The Company does not grant return rights, price protection or pricing adjustments to OEM customers. The Company offers limited contractual stock rotation rights to sell-in distributors. At the time of shipment to sell-in distributors, an allowance for returns is established based upon historical return rates, and an allowance for price adjustments is established based on an estimate of price adjustments to be granted. Actual future returns and price adjustments could be different than the allowance established.
Trade and Other Accounts Receivable, Policy	The Company’s accounts receivable balances represent trade accounts receivables which have been recorded at invoiced amount and do not bear interest.  The Company maintains an allowance for doubtful accounts for estimated uncollectible accounts receivable. This estimate is based on an analysis of specific customer creditworthiness and historical bad debt experience.
Shipping and Handling Cost, Policy	Shipping and handling costs are included in sales and marketing expense and are recognized as period expenses as incurred.
Commitments and Contingencies, Policy	An estimated liability is accrued when it is determined to be probable that a liability has been incurred and the amount of loss can be reasonably estimated. The liability accrual is charged to income in the period such determination is made. Legal fees are expensed as incurred. The Company regularly evaluates current information available to determine whether such accruals should be made.
Research and Development Expense, Policy	Research and development costs are expensed as incurred and consist primarily of payroll and other headcount related costs and cost of materials associated with the development of new wafer fabrication processes and the definition, design and development of semiconductor products. The Company also expenses prototype wafers and new production mask sets related to new products as research and development costs until products based on new designs are released to production.
Self-Insurance, Policy	The Company utilizes third-party insurance carriers subject to varying retention levels of self insurance. The Company is self-insured for a portion of the losses and liabilities primarily associated with earthquake damage, workers’ compensation claims and health benefit claims. Losses are accrued based upon the Company’s estimates of the aggregate liability for claims incurred using historical experience.
Advertising Costs, Policy	The Company expenses advertising costs to selling, general and administrative expense as incurred. Advertising expenses for 2014, 2013 and 2012 were $0.3 million, $0.1 million and $1.0 million, respectively.
Income Tax, Policy	Deferred tax assets and liabilities are recognized for the expected future tax consequences of events that have been reflected in the financial statements. Deferred tax assets and liabilities are determined based on the differences between the book and tax bases of assets and liabilities and operating loss carryforwards, using tax rates expected to be in effect for the years in which the differences are expected to reverse. A valuation allowance is provided to reduce net deferred tax assets if, based upon the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company recognizes the effect of income tax positions only if those positions are more likely than not of being sustained based on the technical merits of the position. The tax benefit of any tax position that meets the more-likely-than-not recognition threshold is calculated at the largest amount that is more than 50% likely of being realized upon resolution of the uncertainty. To the extent a full benefit is not expected to be realized on the uncertain tax position, a reduction to a deferred asset is recorded or an income tax liability is established. Interest and penalties on income tax obligations, including uncertain tax positions, are included in the income tax provision.
Share-based Compensation, Policy	Share-based compensation is measured at the grant date based on the fair value of the award and is recognized over the employee's requisite service period as expense in the consolidated statements of operations. Share-based compensation costs for stock option grants are based on the fair value calculated from a stock option pricing model on the date of grant. The Company has utilized the Black-Scholes option pricing model to determine the fair value for stock option grants.  The fair value of stock option grants is recognized as compensation expense on a straight-line basis over the vesting period of the grants. Compensation expense recognized is shown in the operating activities section of the consolidated statements of cash flows. Cash flows resulting from the tax benefits from tax deductions in excess of the compensation cost recognized (excess tax benefits) is shown in the financing activities section of the consolidated statements of cash flows.
Net Income Per Common and Equivalent Share, Policy	Basic net income per share is computed by dividing net income attributable to Micrel, Incorporated shareholders by the number of weighted-average common shares outstanding. Diluted net income per share reflects potential dilution from outstanding stock options and restricted stock units (“RSUs”) using the treasury stock method.
Fair Value of Financial Instruments, Policy	Financial instruments included in the Company’s consolidated balance sheets at December 31, 2014 and 2013, consist of cash, cash equivalents, accounts receivable, accounts payable and investments. For cash, the carrying amount is the fair value. The carrying amount for cash equivalents, accounts receivable and accounts payable approximates fair value because of the short maturity of those instruments. The fair values of investments are based on quoted market prices, quoted prices for similar assets or valuation models for investments for which quoted market prices are unavailable.

Significant_Accounting_Policie2

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Reconciliation of weighted-average shares used in computing net income per share	Reconciliation of weighted-average shares used in computing basic and diluted net income per share attributable to Micrel, Incorporated shareholders is as follows (in thousands):
		Years Ended December 31,
		2014	2013	2012
	Shares used in computing basic net income per share	56,508	57,803	59,623
	Dilutive effect of stock options and restricted stock units	1,030	703	665
	Shares used in computing diluted net income per share	57,538	58,506	60,288

Investments_Tables

Investments (Tables)	12 Months Ended
	Dec. 31, 2014
Investments [Abstract]
Available-for-sale Securities	A summary of the Company’s short-term investments at December 31, 2014 and 2013 was as follows (in thousands):
		31-Dec-14										31-Dec-13
		Cost			Gross Unrealized		Gross Unrealized			Fair		Cost		Gross Unrealized		Gross Unrealized			Fair
					Gains		Losses			Value				Gains		Losses			Value
	Corporate Debt Securities	$	43,327		$	3	$	(68	)	$	43,262	$	36,947	$	10	$	—		$	36,957
	Commercial Paper	14,975			5		(3		)	14,977		13,991		2		—			13,993
	Municipal Securities	5,191			3		—			5,194		13,858		—		(2		)	13,856
	U.S. Government Agencies Securities	2,000			—		(5		)	1,995		—		—		—			—
	Total	$	65,493		$	11	$	(76	)	$	65,428	$	64,796	$	12	$	(2	)	$	64,806
Available-for-sale Securities, Long Term Investments	A summary of the Company’s long-term investments at December 31, 2014 and December 31, 2013 was as follows (in thousands):
		31-Dec-14										31-Dec-13
		Cost			Gross Unrealized		Gross Unrealized			Fair		Cost		Gross Unrealized		Gross Unrealized			Fair
					Gains		Losses			Value				Gains		Losses			Value
	Auction Rate Notes	$	1,500		$	—	$	(64	)	$	1,436	$	4,700	$	—	$	(505	)	$	4,195
Fair Value, Assets Measured on Recurring Basis	Financial assets and liabilities measured at fair value on a recurring basis were as follows (in thousands):
		31-Dec-14
		Quoted Prices in			Significant Other		Significant			Total
		Active Markets			Observable Inputs		Unobservable
		for Identical			Level 2		Inputs
		Assets					Level 3
		Level 1
	Money Market Funds (1)	$	4,725		$	—	$	—		$	4,725
	Corporate Debt Securities (2)	—			43,262		—			43,262
	Commercial Paper (2)	—			14,977		—			14,977
	Municipal Securities (2)	—			5,194		—			5,194
	U.S. Government Agencies Securities (2)	—			1,995		—			1,995
	Auction-rate notes (3)	—			—		1,436			1,436
	Total	$	4,725		$	65,428	$	1,436		$	71,589
		31-Dec-13
		Quoted Prices in			Significant Other		Significant			Total
		Active Markets			Observable Inputs		Unobservable
		for Identical			Level 2		Inputs
		Assets					Level 3
		Level 1
	Money Market Funds (1)	$	16,945		$	—	$	—		$	16,945
	Corporate Debt Securities (2)	—			36,957		—			36,957
	Commercial Paper (2)	—			13,993		—			13,993
	Municipal Securities (2)	—			13,856		—			13,856
	Auction-rate notes (3)	—			—		4,195			4,195
	Total	$	16,945		$	64,806	$	4,195		$	85,946
	__________
	(1) Included in cash and cash equivalents
	(2) Included in short-term investments
	(3) Included in long-term investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	For the year ended December 31, 2014, the changes in the Company’s Level 3 securities (consisting of auction-rate notes) were as follows (in thousands):
		Fair Value
		Measurements
		Using Significant
		Unobservable
		Inputs
		(Level 3)
	Beginning balance, December 31, 2013	$	4,195
	Transfers in and/or out of Level 3	—
	Total unrealized gains, before tax, included in other comprehensive income	441
	Sales	(3,200		)
	Ending balance, December 31, 2014	$	1,436

Inventories_Tables

Inventories (Tables)	12 Months Ended
	Dec. 31, 2014
Inventory Disclosure [Abstract]
Inventories	Inventories consisted of the following (in thousands):
		December 31,		December 31,
		2014		2013
	Finished goods	$	15,395	$	11,592
	Work in process	27,500		30,109
	Raw materials	1,241		1,500
	Total inventories	$	44,136	$	43,201

Property_Plant_and_Equipment_T

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property, plant and equipment	Property, plant and equipment consisted of the following (in thousands):
		Life	December 31,			December 31,
			2014			2013
	Machinery and equipment	5 years	$	189,335		$	180,851
	Land	—	8,101			8,101
	Buildings and improvements	*	54,483			53,915
	Computer equipment and software	3 years	11,094			11,742
	Office furniture and fixtures	5 years	1,528			1,928
			264,541			256,537
	Accumulated depreciation		(204,088		)	(198,758		)
	Total property, plant and equipment, net		$	60,453		$	57,779

Intangible_Assets_Tables

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Finite-Lived Intangible Assets, Net [Abstract]
Schedule of acquired finite-lived intangible assets by major class	The following table sets forth the components of intangible assets as follows (in thousands):
			December 31, 2014							December 31, 2013
			Gross		Accumulated			Net		Gross		Accumulated			Net
			Carrying		Amortization			Carrying		Carrying		Amortization			Carrying
			Amount					Amount		Amount					Amount
	Developed and core technology		$	7,443	$	(1,810	)	$	5,633	$	7,783	$	(986	)	$	6,797
	Customer relationships		3,800		(1,181		)	2,619		3,800		(552		)	3,248
	Trademarks		610		(370		)	240		610		(284		)	326
	Non-competition agreements		—		—			—		450		(372		)	78
	In-process research and development		1,300		—			1,300		1,300		—			1,300
			$	13,153	$	(3,361	)	$	9,792	$	13,943	$	(2,194	)	$	11,749
Schedule of future amortization expenses	The estimated future amortization expense of intangible assets at December 31, 2014 was as follows (in thousands):
	Year Ending December 31,
	2015	$	1,535
	2016	1,510
	2017	1,281
	2018	1,223
	2019	1,140
	Thereafter	3,103
		$	9,792

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Compensation, Stock Options, Activity	Option activity under the Company’s incentive stock plans is as follows:
			Number			Weighted Avg.
			of Shares			Exercise Price
						Per Share
	Outstanding, December 31, 2011 (3,366,610 shares exercisable at a weighted average price of $10.31 per share and a weighted average remaining contractual life of 4.3 years)		7,960,170			$	10.26
	Granted		1,494,250			10.13
	Exercised		(415,156	)		7.91
	Canceled		(882,995	)		11.22
	Outstanding, December 31, 2012 (4,068,071 shares exercisable at a weighted average price of $9.98 per share and a weighted average remaining contractual life of 4.2 years)		8,156,269			10.25
	Granted		700,300			9.96
	Exercised		(522,218	)		7.62
	Canceled		(821,263	)		10.92
	Outstanding, December 31, 2013 (4,286,232 shares exercisable at a weighted average price of $10.12 per share and a weighted average remaining contractual life of 4.3 years)		7,513,088			10.34
	Granted		445,767			10.85
	Exercised		(1,485,784	)		8.56
	Canceled		(586,132	)		12.38
	Outstanding, December 31, 2014 (3,512,257 shares exercisable at a weighted average price of $10.53 per share and a weighted average remaining contractual life of 4.8 years)		5,886,939			$	10.64
Schedule of Share-based Compensation, Options by Exercise Price Range	Additional information regarding options outstanding at December 31, 2014 was as follows:
			Stock Options Outstanding									Options Exercisable
	Range of Exercise Prices		Number Outstanding			Weighted Avg. Remaining Contractual Life (yrs)		Weighted Avg. Exercise Price Per Share				Number Exercisable	Weighted Avg. Exercise Price Per Share
	$ 4.72 to $ 7.00		132,020			3.5		$	6.63			132,020	$	6.63
	$ 7.01 to $ 7.46		298,340			4.1		7.25				293,380	7.25
	$ 7.49 to $ 8.00		288,283			4.4		7.82				283,803	7.82
	$ 8.01 to $ 9.00		151,588			3.6		8.54				141,785	8.53
	$ 9.01 to $10.00		1,282,671			6.5		9.61				643,954	9.65
	$10.01 to $11.00		1,982,999			6.8		10.41				868,161	10.4
	$11.01 to $13.00		697,258			6		12.09				407,874	12.16
	$13.01 to $16.00		973,780			5.5		13.7				661,280	13.67
	$16.01 to $49.50		80,000			1.2		16.21				80,000	16.21
			5,886,939			5.9		$	10.64			3,512,257	$	10.53
Stock options granted under the Company's option plans, valuation assumptions	The fair value of the stock options granted under the Company’s option plans was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:
		Years Ended December 31,
		2014			2013			2012
	Expected term (years)	6			5.9			5.8
	Stock volatility	30.7	%		34.5	%		36.6	%
	Risk free interest rates	2	%		1.6	%		1	%
	Dividends during expected terms	1.6	%		1.9	%		1.6	%
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	Information with respect to outstanding RSU activity is as follows:
						Weighted
			Number			Average
			of Shares			Grant-Date
						Fair Value
	Outstanding, December 31, 2011		667,277			$	9.73
	Granted		417,531			9.67
	Vested		(146,327	)		9.49
	Forfeited		(61,431	)		9.65
	Outstanding, December 31, 2012		877,050			9.83
	Granted		591,974			9.31
	Vested		(209,819	)		9.6
	Forfeited		(63,943	)		9.69
	Outstanding, December 31, 2013		1,195,262			9.63
	Granted		780,225			10.78
	Vested		(349,451	)		9.61
	Forfeited		(116,935	)		9.89
	Outstanding, December 31, 2014		1,509,101			$	10.21
Share-based compensation expense, period costs	The following table shows total share-based compensation expense recognized in the Consolidated Statements of Operations for the years ended December 31, 2014, 2013 and 2012 (in thousands):
		Years Ended December 31,
		2014				2013				2012
	Cost of revenues	$	997			$	1,060			$	1,178
	Research and development	3,197				2,875				3,132
	Selling, general and administrative	3,430				3,162				3,282
	Pre-tax share-based compensation expense	7,624				7,097				7,592
	Less income tax effect	(2,613		)		(2,314		)		(2,583		)
	Net share-based compensation expense	$	5,011			$	4,783			$	5,009

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of the statutory federal income tax rate to the effective tax rate for the years ended December 31 was as follows:
			2014			2013			2012
	Statutory federal income tax rate		35	%		35	%		35	%
	Research and development credit		(14	)		(22	)		—
	Qualified production activities deduction		(5	)		(3	)		(4	)
	State income taxes (net of federal income tax benefit)		—			—			(2	)
	Non-deductible stock compensation		—			1			1
	Valuation allowance		—			—			27
	Deemed dividend income		—			3			—
	Other *		3			(6	)		(1	)
	Effective tax rate		19	%		8	%		56	%
	* Other, in 2014 and 2013, includes foreign tax rate differential, foreign tax credits and other expenditures not deductible for tax purposes which are all individually insignificant.
Schedule of Components of Income Tax Expense (Benefit)	The provision for income taxes for the years ended December 31, 2014, 2013, and 2012 consisted of the following (in thousands):
			2014				2013				2012
	Current:
	Federal		$	4,869			$	4,833			$	8,847
	State		78				(66		)		(1,731		)
	Foreign		544				494				563
	Total current		5,491				5,261				7,679
	Deferred:
	Federal		(2,179		)		(3,698		)		(8,489		)
	State		(5		)		(31		)		16,901
	Foreign		(140		)		52				(125		)
	Total deferred		(2,324		)		(3,677		)		8,287
	Total provision		$	3,167			$	1,584			$	15,966
Schedule of Deferred Tax Assets and Liabilities	Deferred tax assets and liabilities at December 31, 2014 and 2013 were as follows (in thousands):
			2014				2013
	Deferred tax assets:
	Accruals, reserves and other amounts not currently deductible		$	13,034			$	11,346
	Deferred income		8,106				9,547
	Tax credit carryforwards		12,184				9,170
	Non-qualified share-based compensation		6,245				6,115
	Capitalized research and development		18				—
	Unrealized loss on investments and other		181				278
	Gross deferred tax assets		39,768				36,456
	Valuation allowance		(12,229		)		(8,999		)
	Total deferred tax assets		27,539				27,457
	Deferred tax liabilities:
	Long-lived assets		(3,265		)		(5,187		)
	Foreign undistributed earnings		(18		)		—
	Total deferred tax liability		(3,283		)		(5,187		)
	Net deferred tax assets (current and non-current)		$	24,256			$	22,270
Schedule of Unrecognized Tax Benefits Roll Forward	The amount of unrecognized tax benefits for the years ended December 31 consisted of the following (in thousands):
		2014				2013				2012
	Beginning balance	$	9,433			$	8,259			$	8,532
	Additions based on tax positions related to the current year	909				762				487
	Additions for tax positions related to prior years	662				1,593				77
	Subtractions for tax positions related to prior years and settlements of audits	(4,959		)		(1,181		)		(837		)
	Ending balance	$	6,045			$	9,433			$	8,259

Accrued_Liabilities_Tables

Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2014
Accrued Liabilities [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands):
		December 31,		December 31,
		2014		2013
	Accrued compensation	$	7,050	$	5,767
	Accrued commissions	1,605		1,666
	Accrued restructuring	360		902
	Other accrued liabilities	3,854		4,539
	Total accrued liabilities	$	12,869	$	12,874

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	Future minimum payments under these agreements are as follows (in thousands):
	Year Ending December 31,
	2015	$	960
	2016	526
	2017	420
	2018	120
	2019	21
	Total	$	2,047

Segment_Reporting_Tables

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas
	Geographic Information (in thousands):
		Years Ended December 31,
		2014				2013				2012
		Total Net		Long-Lived		Total Net		Long-Lived		Total Net		Long-Lived
		Revenues		Assets (1)		Revenues		Assets(1)		Revenues		Assets (1)
	United States of America	$	55,574	$	50,125	$	62,667	$	48,432	$	66,267	$	51,715
	Other North American Countries	176		—		144		—		193		—
	Korea	23,324		9		28,050		16		36,896		24
	Taiwan	25,114		3,093		23,503		2,956		22,507		3,492
	Singapore	31,899		9		26,353		9		23,899		8
	China	16,073		1,684		15,873		2,424		16,183		1,417
	Hong Kong	43,060		60		33,881		86		37,300		215
	Japan	16,582		2		14,686		23		14,329		1
	Other Asian Countries	1,377		5,447		1,259		3,727		1,284		3,717
	Europe	34,415		24		30,664		106		31,254		103
	Total	$	247,594	$	60,453	$	237,080	$	57,779	$	250,112	$	60,692
	__________
	(1) Long-lived assets consist of property, plant and equipment.

Restructuring_Tables

Restructuring (Tables)	12 Months Ended
	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Schedule of Restructuring and Related Costs	The following table summarizes the activity related to the accrual for restructuring charges for the year ended December 31, 2014 and 2013 by event (in thousands):
		Plan Initiated in Q4'13			Plan Initiated in Q3'14			Plan Initiated in Q4'14			Total
	Restructuring charges	$	1,376								$	1,376
	Payments	(474		)							(474		)
	Balance at December 31, 2013	902									902
	Restructuring charges	—			631			361			992
	Payments	(882		)	(560		)	(92		)	(1,534		)
	Balance at December 31, 2014	$	20		$	71		$	269		$	360

Supplemental_Quarterly_Financi1

Supplemental Quarterly Financial Summary - Unaudited Supplemental Quarterly Financial Summary - Unaudited (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information [Table Text Block]	SUPPLEMENTAL QUARTERLY FINANCIAL SUMMARY — UNAUDITED
	(in thousands, except per share amounts)	Three Months Ended 2014
		March 31,		June 30,		Sept. 30,		Dec. 31,
	Net revenues	$	59,857	$	62,339	$	67,480	$	57,918
	Gross profit	$	31,219	$	32,791	$	34,408	$	29,610
	Net income (1)	$	2,289	$	3,529	$	4,675	$	3,054
	Net income per share:
	Basic (1)	$	0.04	$	0.06	$	0.08	$	0.05
	Diluted (1)	$	0.04	$	0.06	$	0.08	$	0.05
	Weighted-average shares used in computing
	per share amounts:
	Basic	56,388		56,537		56,642		56,490
	Diluted	57,208		57,448		57,708		57,710
	Cash dividends per common share	$	0.05	$	0.05	$	0.05	$	0.05
	(in thousands, except per share amounts)	Three Months Ended 2013
		March 31,		June 30,		Sept. 30,		Dec. 31,
	Net revenues	$	59,733	$	59,171	$	58,169	$	60,007
	Gross profit	$	31,080	$	31,082	$	29,471	$	30,413
	Net income (2)	$	5,245	$	5,035	$	4,004	$	3,364
	Net income:
	Basic (2)	$	0.09	$	0.09	$	0.07	$	0.06
	Diluted (2)	$	0.09	$	0.09	$	0.07	$	0.06
	Weighted-average shares used in computing
	per share amounts:
	Basic	58,270		58,303		57,752		56,908
	Diluted	59,030		59,007		58,440		57,546
	Cash dividends per common share	$	—	$	0.0425	$	0.05	$	0.05
	__________
	(1) During the third and fourth quarter of 2014, the Company recorded a restructuring charge of $0.5 million and $0.5 million for employee severances and facility closure, respectively.
	(2) During the fourth quarter of 2013, the Company recorded a restructuring charge of $1.4 million for employee severances.

Valuations_and_Qualifying_Acco1

Valuations and Qualifying Accounts Valuation and Qualifying Accounts (Tables)	12 Months Ended
	Dec. 31, 2014
Valuation and Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts [Table Text Block]	MICREL, INCORPORATED
	VALUATION AND QUALIFYING ACCOUNTS
	For the Years Ended December 31, 2014, 2013, and 2012
	(In thousands)
	Description	Balance at Beginning		Allowance Additions or			Returns and Price
		of Year		(Reductions)			Adjustments			Bad Debt			Balance at
										Write-offs			End of Year
	Year Ended December 31, 2014
	Allowances for OEM and sell-in distributor returns and price adjustments	$	737	$	1,970		$	(1,889	)	$	—		$	818
	Allowances for unclaimed sell-through distributor price adjustments (1)	—		64,530			(64,397		)	—			133
	Allowances for doubtful accounts	23		114			—			(30		)	107
	Total allowances	$	760	$	66,614		$	(66,286	)	$	(30	)	$	1,058
	Year Ended December 31, 2013
	Allowances for OEM and sell-in distributor returns and price adjustments	$	712	$	1,954		$	(1,929	)	$	—		$	737
	Allowances for unclaimed sell-through distributor price adjustments (1)	51		77,129			(77,180		)	—			—
	Allowances for doubtful accounts	49		(26		)	—			—			23
	Total allowances	$	812	$	79,057		$	(79,109	)	$	—		$	760
	Year Ended December 31, 2012
	Allowances for OEM and sell-in distributor returns and price adjustments	$	1,066	$	1,452		$	(1,806	)	$	—		$	712
	Allowances for unclaimed sell-through distributor price adjustments (1)	169		73,674			(73,792		)	—			51
	Allowances for doubtful accounts	59		(10		)	—			—			49
	Total allowances	$	1,294	$	75,116		$	(75,598	)	$	—		$	812
	___________
	(1) The Company estimates and records an allowance for sell-through distributor price adjustments for which the specific resale transaction has been completed, but the price adjustment claim has not yet been received from the sell-through distributor. This allowance typically represents approximately one to three weeks of unclaimed price adjustments.

Significant_Accounting_Policie3

Significant Accounting Policies Investments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accounting Policies [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax	($83)	($320)

Significant_Accounting_Policie4

Significant Accounting Policies Certain Significant Risks (Details) (Customer Concentration Risk [Member], Accounts Receivable [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Distributor A [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	24.00%	36.00%
Distributor C [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	15.00%
Distributor B [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	13.00%	11.00%

Significant_Accounting_Policie5

Significant Accounting Policies Impairment of long-lived assets (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Impaired Intangible Assets [Abstract]
Goodwill, Impairment Loss	$0	$0	$0
Impairment of technology	0	0	1,000,000
Research and Development Expense [Member]
Impaired Intangible Assets [Abstract]
Impairment of technology			$1,000,000

Significant_Accounting_Policie6

Significant Accounting Policies Revenue Recognition (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Accounting Policies [Abstract]
Amount of one-time increase in revenue from conversion of distributors to sell-in revenue recognition method	$5.10
Amount of one-time increase in cost of goods sold from conversion of distributors to sell-in revenue recognition method	$1.60

Significant_Accounting_Policie7

Significant Accounting Policies Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Asset Impairment Charges	$0	$0
Advertising expenses	$300,000	$100,000	$1,000,000

Net_Income_Per_Share_Details

Net Income Per Share (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of weighted-average shares used in computing net income per share
Shares used in computing basic net income per share	56,490,000	56,642,000	56,537,000	56,388,000	56,908,000	57,752,000	58,303,000	58,270,000	56,508,000	57,803,000	59,623,000
Dilutive effect of stock options and restricted stock units									1,030,000	703,000	665,000
Shares used in computing diluted net income per share	57,710,000	57,708,000	57,448,000	57,208,000	57,546,000	58,440,000	59,007,000	59,030,000	57,538,000	58,506,000	60,288,000
Stock options excluded from the weighted-average number of common shares outstanding for the diluted net income per share computations as they were anti-dilutive									2,700,000	5,400,000	5,200,000

Acquisitions_Details_Textual

Acquisitions (Details Textual) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 09, 2013	Aug. 30, 2013	Dec. 20, 2012	Apr. 02, 2012
Business Acquisition [Line Items]
Payments to acquire remaining noncontrolling interest	$0	$6,122,000	$0
Discera, Inc. [Member]
Business Acquisition [Line Items]
Date of acquisition agreement					30-Aug-13
Acquisition effective date				9-Sep-13
Total purchase price				7,200,000
Short-term debt				-1,100,000
Business Acquisition, Cash paid at closing				6,100,000
Business Acquisition, Cash Withheld				1,100,000
Payment of restricted cash	1,000,000
Goodwill, Other Changes	100,000
Goodwill	2,600,000
PhaseLink Acquisition [Member]
Business Acquisition [Line Items]
Acquisition effective date							2-Apr-12
Percentage of outstanding shares acquired						5.00%	95.00%
Total purchase price							19,700,000
Payments to acquire remaining noncontrolling interest						900,000
Resulting ownership percentage in PhaseLink						100.00%
Business Acquisition, Cash paid at closing							$16,400,000
Customer relationships [Member] | Discera, Inc. [Member]
Business Acquisition [Line Items]
Identifiable intangible assets estimated useful life	3 years
Customer relationships [Member] | PhaseLink Acquisition [Member]
Business Acquisition [Line Items]
Identifiable intangible assets estimated useful life	10 years
Noncompete Agreements [Member] | Discera, Inc. [Member]
Business Acquisition [Line Items]
Identifiable intangible assets estimated useful life	1 year
Noncompete Agreements [Member] | PhaseLink Acquisition [Member]
Business Acquisition [Line Items]
Identifiable intangible assets estimated useful life	2 years
Trademarks [Member] | Discera, Inc. [Member]
Business Acquisition [Line Items]
Identifiable intangible assets estimated useful life	10 years
Developed Technology Rights [Member] | Discera, Inc. [Member]
Business Acquisition [Line Items]
Identifiable intangible assets estimated useful life	10 years
Developed Technology Rights [Member] | PhaseLink Acquisition [Member]
Business Acquisition [Line Items]
Identifiable intangible assets estimated useful life	10 years
Minimum [Member] | Trademarks [Member] | PhaseLink Acquisition [Member]
Business Acquisition [Line Items]
Identifiable intangible assets estimated useful life	2 years
Maximum [Member] | Trademarks [Member] | PhaseLink Acquisition [Member]
Business Acquisition [Line Items]
Identifiable intangible assets estimated useful life	5 years

Acquisitions_Details

Acquisitions (Details) (USD $)	Dec. 31, 2014	Sep. 09, 2013	Apr. 02, 2012
In Millions, unless otherwise specified
Discera, Inc. [Member]
Business Acquisition [Line Items]
Goodwill	$2.60
Short-term debt		-1.1
Total purchase price		7.2
PhaseLink Acquisition [Member]
Business Acquisition [Line Items]
Total purchase price			$19.70

Investments_Details

Investments (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Short-term investments in a continuous unrealized loss position, twelve months or longer	$0
Accumulated Other Comprehensive Income (Loss), Net of Tax	-83,000	-320,000
Gross Unrealized Losses	-76,000	-2,000
Gross Unrealized Gains	11,000	12,000
Fair Value	65,428,000	64,806,000
Cost	65,493,000	64,796,000
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses	-3,000	0
Gross Unrealized Gains	5,000	2,000
Fair Value	14,977,000	13,993,000
Cost	14,975,000	13,991,000
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses	-68,000	0
Gross Unrealized Gains	3,000	10,000
Fair Value	43,262,000	36,957,000
Cost	43,327,000	36,947,000
Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses	0	-2,000
Gross Unrealized Gains	3,000	0
Fair Value	5,194,000	13,856,000
Cost	5,191,000	13,858,000
Auction Rate Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Auction Rate Notes Sold	3,200,000
Gross Unrealized Losses	-64,000	-505,000
Gross Unrealized Gains	0	0
Fair Value	1,436,000	4,195,000
Cost	1,500,000	4,700,000
Available-for-sale Securities, Amortized Cost Basis	1,500,000
U.S. Government Agencies Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses	-5,000	0
Gross Unrealized Gains	0	0
Fair Value	1,995,000	0
Cost	$2,000,000	$0

Investments_Fair_Value_Measure

Investments Fair Value Measurements (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	$71,589,000	[1]	$85,946,000
Short-term interest rate reset dates of auction rate note securities	less than ninety days
Auction rate note securities with contractual maturities	excess of ten years
Period for principal repayments	33 years
Reset period for the securities held	seven or twenty eight days
Comprehensive income (loss) net of tax due to auction rate notes	237,000		212,000		355,000
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	4,725,000	[2]	16,945,000	[2]
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	43,262,000	[3]	36,957,000
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	14,977,000	[3]	13,993,000
Auction Rate Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	1,436,000	[1]	4,195,000
Interest rate, percent in excess of one month LIBOR	1.50%
Comprehensive income (loss) before tax due to auction rate notes	-100,000
Comprehensive income (loss) net of tax due to auction rate notes	-100,000
Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	5,194,000	[3]	13,856,000
U.S. Government Agencies Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	1,995,000	[3]
Quoted Prices in Active Markets for Identical Assets Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	4,725,000	[1]	16,945,000	[1]
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	4,725,000	[2]	16,945,000	[2]
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	0	[3]	0	[3]
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	0	[3]	0	[3]
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Auction Rate Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	0	[1]	0	[1]
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	0	[3]	0	[3]
Quoted Prices in Active Markets for Identical Assets Level 1 [Member] | U.S. Government Agencies Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	0	[3]
Significant Other Observable Inputs Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	65,428,000	[1]	64,806,000	[1]
Significant Other Observable Inputs Level 2 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	0	[2]	0	[2]
Significant Other Observable Inputs Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	43,262,000	[3]	36,957,000	[3]
Significant Other Observable Inputs Level 2 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	14,977,000	[3]	13,993,000	[3]
Significant Other Observable Inputs Level 2 [Member] | Auction Rate Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	0	[1]	0	[1]
Significant Other Observable Inputs Level 2 [Member] | Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	5,194,000	[3]	13,856,000	[3]
Significant Other Observable Inputs Level 2 [Member] | U.S. Government Agencies Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	1,995,000	[3]
Significant Unobservable Inputs Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	1,436,000		4,195,000
Transfers in and/or out of Level 3	0
Total gains, before tax	441,000
Settlements	-3,200,000
Financial assets and liabilities measured at fair value on a recurring basis	1,436,000	[1]	4,195,000	[1]
Significant Unobservable Inputs Level 3 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	0		0	[2]
Significant Unobservable Inputs Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	0	[3]	0	[3]
Significant Unobservable Inputs Level 3 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	0	[3]	0	[3]
Significant Unobservable Inputs Level 3 [Member] | Auction Rate Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	1,436,000	[1]	4,195,000	[1]
Significant Unobservable Inputs Level 3 [Member] | Municipal Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	0	[3]	0	[3]
Significant Unobservable Inputs Level 3 [Member] | U.S. Government Agencies Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities measured at fair value on a recurring basis	$0	[3]
[1]	Included in long-term investments
[2]	Included in cash and cash equivalents
[3]	Included in short-term investments

Inventories_Details

Inventories (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]
Finished goods	$15,395	$11,592
Work in process	27,500	30,109
Raw materials	1,241	1,500
Inventories
Total inventories	$44,136	$43,201

Property_Plant_and_Equipment_D

Property, Plant and Equipment (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, plant and equipment
Property, plant and equipment, Gross	$264,541	$256,537
Accumulated depreciation	-204,088	-198,758
Total property, plant and equipment, net	60,453	57,779
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Property, plant and equipment
Property, plant and equipment, Gross	189,335	180,851
Land [Member]
Property, plant and equipment
Property, plant and equipment, Gross	8,101	8,101
Buildings and improvements [Member]
Property, plant and equipment
Property, plant and equipment, Gross	54,483	53,915
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Property, plant and equipment
Property, plant and equipment, Gross	11,094	11,742
Office furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Property, plant and equipment
Property, plant and equipment, Gross	$1,528	$1,928
Minimum [Member] | Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Maximum [Member] | Buildings and improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	30 years

Property_Plant_and_Equipment_D1

Property, Plant and Equipment (Details Textual) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Capital Expenditures Incurred but Not yet Paid	$3	$1
Property, Plant and Equipment (Textual) [Abstract]
Depreciation	$11	$11.10	$11.50

Intangible_Assets_Details_Text

Intangible Assets (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$1,600,000	$1,400,000	$800,000
Impairment of technology	0	0	1,000,000
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	10 years
Research and Development Expense [Member]
Finite-Lived Intangible Assets [Line Items]
Impairment of technology			1,000,000
Discera, Inc. [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired		2,700,000
PhaseLink Acquisition [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired			8,300,000
Other Acquired Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired		$2,100,000

Finitelived_Intangible_Assets_

Finite-lived Intangible Assets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$13,153	$13,943
Accumulated Amortization	-3,361	-2,194
Net Carrying Amount	9,792	11,749
Developed and core technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,443	7,783
Accumulated Amortization	-1,810	-986
Net Carrying Amount	5,633	6,797
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,800	3,800
Accumulated Amortization	-1,181	-552
Net Carrying Amount	2,619	3,248
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	610	610
Accumulated Amortization	-370	-284
Net Carrying Amount	240	326
Non-competition agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	0	450
Accumulated Amortization	0	-372
Net Carrying Amount	0	78
In-process research and development [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,300	1,300
Accumulated Amortization	0	0
Net Carrying Amount	$1,300	$1,300

Intangible_Assets_Details

Intangible Assets (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of future amortization expenses
2015	$1,535
2016	1,510
2017	1,281
2018	1,223
2019	1,140
Thereafter	3,103
Net Carrying Amount	$9,792	$11,749

Borrowing_Arrangements_Details

Borrowing Arrangements (Details) (USD $)	0 Months Ended	12 Months Ended
	Apr. 02, 2012	Dec. 31, 2014	Jun. 30, 2012
	Term_Loans
Line of Credit Facility [Line Items]
Line of Credit Facility, Amount Outstanding		$0
Letters of credit outstanding		300,000
Borrowing Arrangements (Additional Textual) [Abstract]
Line of credit available for general working capital needs		5,000,000
Letter of credit sub-facility		5,000,000
Foreign exchange sub-facility		2,000,000
Number of term loans under acquisition	2
Line of Credit Facility, Description		Interest rates under the facility are based on one of three interest rates, at the Company’s option: (1) a variable alternate base rate plus 1.0%, the alternate base rate being the greater of (x) Bank of the West’s prime rate, (y) the Fed Funds Rate plus 0.5% or (z) daily adjusted one-month LIBOR plus 1.0%; (2) floating one-month LIBOR plus 2.0% or (3) fixed LIBOR for one, two, three or six month periods, plus 2.0%.
PhaseLink Acquisition [Member]
Borrowing Arrangements (Additional Textual) [Abstract]
Loans acquired with local bank in Taiwan	300,000		$0

Shareholders_Equity_and_ShareB1

Shareholders' Equity and Share-Based Compensation Narrative (Details) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	24-May-12
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Shares Authorized	5,000,000	5,000,000
Share Repurchase Program [Abstract]
Stock Repurchase Program, Authorized Amount	$145
Stock Repurchase Program, Remaining Authorized Repurchase Amount	30.7
Stock Repurchased During Period, Shares	1,700,000
Stock Repurchased During Period, Value	20.2
Share Repurchases Pending Cash Settlement	0.2
Incentive Award Plans [Abstract]
Options exercisable and expected to vest	5,172,424
Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	5 years 8 months 1 day
Estimated intrinsic value of options exercisable and expected to vest	20.3
Weighted average fair values of options granted	$2.93	$2.86	$2.96
Aggregate intrinsic value of options exercised	4.2	1.2	1
Cash Received from Exercise of Stock Options	12.7	4	3.3
Excess tax benefit realized from exercise of non-qualified stock options and disqualifying dispositions of incentive stock options	2	0.5	0.2
Share Price	$14.51
Intrinsic value of outstanding options	22.9
Intrinsic value of exercisable options	14.1
Capitalized share-based compensation included in inventory	0.2	0.2
Nonvested Awards, Compensation Not yet Recognized, Stock Options	4.8
Employee Stock Purchase Plan [Abstract]
Stock issued during the period under the plan	100,000	100,000	100,000
Weighted average purchase price per share of shares purchased	$11.43	$9.32	$9.40
2012 Equity Incentive Award Plan [Member]
Incentive Award Plans [Abstract]
Reduction in shares available for issuance under the current plan for shares issued under the prior plan	2
Number of shares reserved for future issuance				6,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	3,400,000
Employee Stock Purchase Plan [Member]
Employee Stock Purchase Plan [Abstract]
Discounted market value of stock, percent	95.00%
Number of shares reserved for issuance under the plan	2,000,000
Employee Stock Option [Member]
Incentive Award Plans [Abstract]
Compensation cost not yet recognized, period for recognition	2 years 5 months 10 days
Employee Stock Option [Member] | 2012 Equity Incentive Award Plan [Member]
Incentive Award Plans [Abstract]
Term of stock option grant	10 years
Restricted Stock Units (RSUs) [Member]
Incentive Award Plans [Abstract]
RSUs expected to vest	1,300,000
RSUs, Outstanding, Weighted Average Remaining Contractual Terms	2 years 8 months 1 day
RSUs, Aggregate Intrinsic Value, Nonvested	19.2
Aggregate intrinsic value of RSU's expected to vest	10.8
Aggregate Intrinsic Value of Vested RSUs	$4
Compensation cost not yet recognized, period for recognition	2 years 10 months 20 days
Vesting in Four Equal Installments [Member] | Restricted Stock Units (RSUs) [Member]
Incentive Award Plans [Abstract]
Vesting percentage	83.00%
Vesting Period	4 years
Vesting One-Third Annually Beginning Third Anniversary of Grant Date [Member] | Restricted Stock Units (RSUs) [Member]
Incentive Award Plans [Abstract]
Vesting percentage	14.00%
Minimum [Member] | Annual Vesting Percentage [Member] | Employee Stock Option [Member] | 2012 Equity Incentive Award Plan [Member]
Incentive Award Plans [Abstract]
Vesting percentage	20.00%
Maximum [Member] | Annual Vesting Percentage [Member] | Employee Stock Option [Member] | 2012 Equity Incentive Award Plan [Member]
Incentive Award Plans [Abstract]
Vesting percentage	25.00%

Shareholders_Equity_and_ShareB2

Shareholders' Equity and Share-Based Compensation Stock Option Activity (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning, options	7,513,088	8,156,269	7,960,170
Granted, options	445,767	700,300	1,494,250
Exercised, options	-1,485,784	-522,218	-415,156
Canceled, options	-586,132	-821,263	-882,995
Outstanding, ending, options	5,886,939	7,513,088	8,156,269
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning, weighted average exercise price	$10.34	$10.25	$10.26
Granted, weighted average exercise price	$10.85	$9.96	$10.13
Exercised, weighted average exercise price	$8.56	$7.62	$7.91
Canceled, weighted average exercise price	$12.38	$10.92	$11.22
Outstanding, ending, weighted average exercise price	$10.64	$10.34	$10.25
Exercisable, options	3,512,257	4,286,232	4,068,071		3,366,610
Exercisable, options, weighted average exercise price	$10.53	$10.12	$9.98		$10.31
Exercisable, options, weighted average remaining contractual life	4 years 9 months 1 day	4 years 3 months 20 days	4 years 2 months 13 days	4 years 3 months 20 days

ShareBased_Compensation_Detail

Share-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Number of Outstanding Options	5,886,939
Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	5 years 11 months
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$10.64
Exercise Price Range, Number of Exercisable Options	3,512,257
Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$10.53
Stock Options [Member] | Range One [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$4.72
Exercise Price Range, Upper Range Limit	$7
Exercise Price Range, Number of Outstanding Options	132,020
Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	3 years 5 months 19 days
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$6.63
Exercise Price Range, Number of Exercisable Options	132,020
Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$6.63
Stock Options [Member] | Range Two [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$7.01
Exercise Price Range, Upper Range Limit	$7.46
Exercise Price Range, Number of Outstanding Options	298,340
Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	4 years 1 month
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$7.25
Exercise Price Range, Number of Exercisable Options	293,380
Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$7.25
Stock Options [Member] | Range Three [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$7.49
Exercise Price Range, Upper Range Limit	$8
Exercise Price Range, Number of Outstanding Options	288,283
Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	4 years 5 months
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$7.82
Exercise Price Range, Number of Exercisable Options	283,803
Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$7.82
Stock Options [Member] | Range Four [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$8.01
Exercise Price Range, Upper Range Limit	$9
Exercise Price Range, Number of Outstanding Options	151,588
Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	3 years 7 months
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$8.54
Exercise Price Range, Number of Exercisable Options	141,785
Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$8.53
Stock Options [Member] | Range Five [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$9.01
Exercise Price Range, Upper Range Limit	$10
Exercise Price Range, Number of Outstanding Options	1,282,671
Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	6 years 6 months
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$9.61
Exercise Price Range, Number of Exercisable Options	643,954
Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$9.65
Stock Options [Member] | Range Six [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$10.01
Exercise Price Range, Upper Range Limit	$11
Exercise Price Range, Number of Outstanding Options	1,982,999
Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	6 years 9 months
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$10.41
Exercise Price Range, Number of Exercisable Options	868,161
Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$10.40
Stock Options [Member] | Range Seven [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$11.01
Exercise Price Range, Upper Range Limit	$13
Exercise Price Range, Number of Outstanding Options	697,258
Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	6 years 0 months
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$12.09
Exercise Price Range, Number of Exercisable Options	407,874
Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$12.16
Stock Options [Member] | Range Eight [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$13.01
Exercise Price Range, Upper Range Limit	$16
Exercise Price Range, Number of Outstanding Options	973,780
Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	5 years 6 months
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$13.70
Exercise Price Range, Number of Exercisable Options	661,280
Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$13.67
Stock Options [Member] | Range Nine [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$16.01
Exercise Price Range, Upper Range Limit	$49.50
Exercise Price Range, Number of Outstanding Options	80,000
Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	1 year 2 months
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$16.21
Exercise Price Range, Number of Exercisable Options	80,000
Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$16.21

Shareholders_Equity_and_ShareB3

Shareholders' Equity and Share-Based Compensation Restricted Stock Activity (Details) (Restricted Stock Units (RSUs) [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding, beginning, restricted stock units	1,195,262	877,050	667,277
Granted, restricted stock units	780,225	591,974	417,531
Vested, restricted stock units	-349,451	-209,819	-146,327
Forfeited, restricted stock units	-116,935	-63,943	-61,431
Outstanding, ending, restricted stock units	1,509,101	1,195,262	877,050
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding, beginning, weighted average grant date fair value	$9.63	$9.83	$9.73
Granted, weighted average grant date fair value	$10.78	$9.31	$9.67
Vested, weighted average grant date fair value	$9.61	$9.60	$9.49
Forfeited, weighted average grant date fair value	$9.89	$9.69	$9.65
Outstanding, ending, weghted average grant date fair value	$10.21	$9.63	$9.83

Shareholders_Equity_and_ShareB4

Shareholders' Equity and Share-Based Compensation Option Assumptions (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock options granted under the Company's option plans
Expected term	6 years 0 months 0 days	5 years 10 months 29 days	5 years 9 months 22 days
Stock volatility	30.70%	34.50%	36.60%
Risk free interest rates	2.00%	1.60%	1.00%
Dividends during expected terms	1.60%	1.90%	1.60%

ShareBased_Compensation_Period

Share-Based Compensation, Period Costs (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based compensation expense
Share-based compensation	$7,624	$7,097	$7,592
Less income tax effect	-2,613	-2,314	-2,583
Net Share-based Compensation Expense	5,011	4,783	5,009
Cost of revenues [Member]
Share-based compensation expense
Share-based compensation	997	1,060	1,178
Research and development [Member]
Share-based compensation expense
Share-based compensation	3,197	2,875	3,132
Selling, general and administrative [Member]
Share-based compensation expense
Share-based compensation	$3,430	$3,162	$3,282

Income_Taxes_Income_Tax_Rate_R

Income Taxes Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Statutory federal income tax rate	35.00%		35.00%	35.00%
Research and development credit	-14.00%		-22.00%	0.00%
Qualified production activities deduction	-5.00%		-3.00%	-4.00%
State income taxes (net of federal income tax benefit)	0.00%		0.00%	-2.00%
Non-deductible stock compensation	0.00%		1.00%	1.00%
Valuation allowance	0.00%		0.00%	27.00%
Deemed dividend income	0.00%		3.00%	0.00%
Other	3.00%	[1]	-6.00%	-1.00%
Effective tax rate	19.00%		8.00%	56.00%
[1]	Other, in 2014 and 2013, includes foreign tax rate differential, foreign tax credits and other expenditures not deductible for tax purposes which are all individually insignificant.

Income_Taxes_Components_of_Inc

Income Taxes Components of Income Tax Expense (Benefit) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current:
Federal	$4,869	$4,833	$8,847
State	78	-66	-1,731
Foreign	544	494	563
Total current	5,491	5,261	7,679
Deferred:
Federal	-2,179	-3,698	-8,489
State	-5	-31	16,901
Foreign	-140	52	-125
Total deferred	-2,324	-3,677	8,287
Total provision	$3,167	$1,584	$15,966

Income_Taxes_Details_Textual

Income Taxes (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pre-tax income from U.S. jurisdiction	$16,600,000	$16,900,000	$28,000,000
Pre-tax income from foreign jurisdictions	100,000	2,300,000	300,000
Deferred Tax Assets, Net, Current	24,300,000
Deferred Tax Assets, Valuation Allowance	12,229,000	8,999,000
Liability for Uncertain Tax Positions, Current	7,600,000
Net amount, reduced for the federal effects of potential state tax exposures	6,000,000
Net amount, favorably affect the company's tax provision in future periods	3,500,000
Increase in deferred tax assets, uncertain tax positions	2,500,000
Liability for uncertain tax positions in long term taxes payable	3,511,000	3,575,000
Unrecognized Tax Benefits, Recognized in Current Period from Lapse of Statute of Limitations	4,900,000
Income Tax Examination, Interest Accrued	300,000	300,000
State and Local Jurisdiction [Member]
Deferred Tax Assets, Tax Credit Carryforwards, Research	22,100,000
Current Income Taxes Payable [Member]
Income Tax Examination, Interest Accrued	55,000
Long-Term Income Taxes Payable [Member]
Income Tax Examination, Interest Accrued	$3,500,000

Income_Taxes_Deferred_Income_T

Income Taxes Deferred Income Tax Assets and Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred tax assets:
Accruals, reserves and other amounts not currently deductible	$13,034	$11,346
Deferred income	8,106	9,547
Tax credit carryforwards	12,184	9,170
Non-qualified share-based compensation	6,245	6,115
Capitalized research and development	18	0
Unrealized loss on investments and other	181	278
Gross deferred tax assets	39,768	36,456
Valuation allowance	-12,229	-8,999
Total deferred tax assets	27,539	27,457
Deferred tax liabilities:
Long-lived assets	-3,265	-5,187
Foreign undistributed earnings	-18	0
Total deferred tax liability	-3,283	-5,187
Net deferred tax assets (current and non-current)	$24,256	$22,270

Income_Taxes_Uncertain_Tax_Pos

Income Taxes Uncertain Tax Positions (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$9,433	$8,259	$8,532
Additions based on tax positions related to the current year	909	762	487
Additions for tax positions related to prior years	662	1,593	77
Subtractions for tax positions related to prior years and settlements of audits	-4,959	-1,181	-837
Ending balance	$6,045	$9,433	$8,259

Accrued_Liabilities_Details

Accrued Liabilities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accrued Liabilities [Abstract]
Accrued compensation	$7,050	$5,767
Accrued commissions	1,605	1,666
Accrued restructuring	360	902
Other accrued liabilities	3,854	4,539
Accrued Liabilities, Current	$12,869	$12,874

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	12 Months Ended					3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2007	Dec. 31, 2006	Jun. 30, 2012	Mar. 31, 2012
Loss Contingencies [Line Items]
Nadatel purchased low-dropout voltage regulators				17,000	17,000
2015	$960,000
2016	526,000
2017	420,000
2018	120,000
2019	21,000
Total	2,047,000
Rent expense under operating leases	1,100,000	1,100,000	1,100,000
Open purchase orders	19,400,000
Letters of credit outstanding	300,000
Selling, general and administrative [Member]
Loss Contingencies [Line Items]
Settlement expense						$200,000	$200,000

ProfitSharing_401k_Plan_Detail

Profit-Sharing 401(k) Plan (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation and Retirement Disclosure [Abstract]
Service requirement for eligibility in the plan	1 month
Defined Contribution Plan, Minimum Annual Contribution By Employee, Percent	1.00%
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent	15.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount Accrued	$0.40
Employer's discretionary annual contribution to the plan		$0.20	$0.40
Ratable vesting period for employer's contributuions to the plan	6 years

Segment_Reporting_Details

Segment Reporting (Details) (Customer Concentration Risk [Member], Sales [Member])	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Original Equipment Manufacturer [Member]
Revenue from External Customer [Line Items]
Concentration Risk, Number of Significant Customers	0	0	1
Concentration risk, percentage	10.00%	10.00%	10.00%
Distributor A [Member]
Revenue from External Customer [Line Items]
Concentration risk, percentage	25.00%	29.00%	22.00%
Distributor B [Member]
Revenue from External Customer [Line Items]
Concentration risk, percentage	18.00%	17.00%	15.00%

Segment_Reporting_Geographic_I

Segment Reporting Geographic Information (Details) (USD $)	3 Months Ended										12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Net Revenues	$57,918		$67,480	$62,339	$59,857	$60,007		$58,169	$59,171	$59,733	$247,594		$237,080		$250,112
Long-Lived Assets (1)	60,453	[1]				57,779	[1]				60,453	[1]	57,779	[1]	60,692	[1]
United States of America
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Net Revenues											55,574		62,667		66,267
Long-Lived Assets (1)	50,125					48,432					50,125		48,432		51,715
Other North American Countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Net Revenues											176		144		193
Long-Lived Assets (1)	0					0					0		0		0
Korea
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Net Revenues											23,324		28,050		36,896
Long-Lived Assets (1)	9					16					9		16		24
Taiwan
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Net Revenues											25,114		23,503		22,507
Long-Lived Assets (1)	3,093					2,956					3,093		2,956		3,492
Singapore
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Net Revenues											31,899		26,353		23,899
Long-Lived Assets (1)	9					9					9		9		8
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Net Revenues											16,073		15,873		16,183
Long-Lived Assets (1)	1,684					2,424					1,684		2,424		1,417
Hong Kong
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Net Revenues											43,060		33,881		37,300
Long-Lived Assets (1)	60					86					60		86		215
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Net Revenues											16,582		14,686		14,329
Long-Lived Assets (1)	2					23					2		23		1
Other Asian Countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Net Revenues											1,377		1,259		1,284
Long-Lived Assets (1)	5,447					3,727					5,447		3,727		3,717
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Net Revenues											34,415		30,664		31,254
Long-Lived Assets (1)	$24					$106					$24		$106		$103
[1]	Long-lived assets consist of property, plant and equipment.

Dividends_Details

Dividends (Details) (USD $)	0 Months Ended	12 Months Ended
	Dec. 27, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Dividends, Common Stock [Abstract]
Payment of cash dividends		$11,299,000	$8,219,000	$12,072,000
Dividends paid per common share		$0.20	$0.14	$0.21
Accelerated cash dividend per share	$0.04
Payment of accelerated cash dividends	$2,500,000

Restructuring_Details

Restructuring (Details) (USD $)	3 Months Ended			12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$500	$500	$1,400	$992	$1,376	$0
Payments for Restructuring				-1,534	-474
Accrued restructuring	360		902	360	902
Q42013 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges				0	1,376
Payments for Restructuring				-882	-474
Accrued restructuring	20		902	20	902
Q32014 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges				631
Payments for Restructuring				-560
Accrued restructuring	71			71
Q42014 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges				361
Payments for Restructuring				-92
Accrued restructuring	$269			$269

Subsequent_Event_Details

Subsequent Event (Details) (USD $)	0 Months Ended
	Jan. 30, 2014	Feb. 26, 2015	Feb. 12, 2015
Subsequent Event [Line Items]
Dividends Payable, Date Declared	29-Jan-15
Dividends, Declared, Per Share	$0.05
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends Payable, Date to be Paid		25-Feb-15
Dividends Payable, Date of Record			11-Feb-15

Supplemental_Quarterly_Financi2

Supplemental Quarterly Financial Summary - Unaudited (Details) (USD $)	3 Months Ended																12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Total Net Revenues	$57,918		$67,480		$62,339		$59,857		$60,007		$58,169		$59,171		$59,733		$247,594	$237,080	$250,112
Gross Profit	29,610		34,408		32,791		31,219		30,413		29,471		31,082		31,080		128,028	122,046	132,927
Net income	3,054	[1]	4,675	[1]	3,529	[1]	2,289	[1]	3,364	[2]	4,004	[2]	5,035	[2]	5,245	[2]	13,547	17,648	12,328
Earnings Per Share, Basic	$0.05	[1]	$0.08	[1]	$0.06	[1]	$0.04	[1]	$0.06	[2]	$0.07	[2]	$0.09	[2]	$0.09	[2]	$0.24	$0.31	$0.21
Earnings Per Share, Diluted	$0.05	[1]	$0.08	[1]	$0.06	[1]	$0.04	[1]	$0.06	[2]	$0.07	[2]	$0.09	[2]	$0.09	[2]	$0.24	$0.30	$0.20
Shares used in computing basic net income per share	56,490		56,642		56,537		56,388		56,908		57,752		58,303		58,270		56,508	57,803	59,623
Weighted Average Number of Shares Outstanding, Diluted	57,710		57,708		57,448		57,208		57,546		58,440		59,007		59,030		57,538	58,506	60,288
Common Stock, Dividends, Per Share, Declared	$0.05		$0.05		$0.05		$0.05		$0.05		$0.05		$0.04		$0		$0.20	$0.14	$0.21	[3]
Restructuring charges	$500		$500						$1,400								$992	$1,376	$0
[1]	During the third and fourth quarter of 2014, the Company recorded a restructuring charge of $0.5 million and $0.5 million for employee severances and facility closure, respectively.
[2]	During the fourth quarter of 2013, the Company recorded a restructuring charge of $1.4 million for employee severances.
[3]	Included an accelerated cash dividend of $0.0425 per share of common stock totaling $2.5 million paid on December 27, 2012 to shareholders of record as of December 18, 2012.

Valuations_and_Qualifying_Acco2

Valuations and Qualifying Accounts (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$760		$812		$1,294
Allowance Additions or (Reductions)	66,614		79,057		75,116
Returns and Price Adjustments	-66,286		-79,109		-75,598
Bad Debt Write-offs	-30		0		0
Balance at End of Year	1,058		760		812
OEM and Stocking Representative Returns and Price Adjustments [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	737		712		1,066
Allowance Additions or (Reductions)	1,970		1,954		1,452
Returns and Price Adjustments	-1,889		-1,929		-1,806
Bad Debt Write-offs	0		0		0
Balance at End of Year	818		737		712
Unclaimed Distributor Price Adjustments [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	0	[1]	51	[1]	169	[1]
Allowance Additions or (Reductions)	64,530	[1]	77,129	[1]	73,674	[1]
Returns and Price Adjustments	-64,397	[1]	-77,180	[1]	-73,792	[1]
Bad Debt Write-offs	0	[1]	0	[1]	0	[1]
Balance at End of Year	133	[1]	0	[1]	51	[1]
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	23		49		59
Allowance Additions or (Reductions)	114		-26		-10
Returns and Price Adjustments	0		0		0
Bad Debt Write-offs	-30		0		0
Balance at End of Year	$107		$23		$49
[1]	The Company estimates and records an allowance for sell-through distributor price adjustments for which the specific resale transaction has been completed, but the price adjustment claim has not yet been received from the sell-through distributor. This allowance typically represents approximately one to three weeks of unclaimed price adjustments.