Earn-out on acquisition date

No definition available.

Name:	atml_Earnoutonacquisitiondate
Namespace Prefix:	atml_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

NMI goodwill - Deductible for Tax

+ References

No definition available.

+ Details

Name:	atml_NMIgoodwillDeductibleforTax
Namespace Prefix:	atml_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

NMI potential earn-out

+ References

No definition available.

+ Details

Name:	atml_NMIpotentialearnout
Namespace Prefix:	atml_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e1043-128460

+ Details

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

For transactions that are recognized separately from the acquisition of assets and assumptions of liabilities in the business combination, such as related to pre-existing relationships with the acquiree, this element represents the disclosure of the amount of acquisition related costs which have been expensed.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresAcquisitionCostExpensed
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 16

-URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e961-128460

+ Details

Name:	us-gaap_GoodwillPurchaseAccountingAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=atml_AcquisitionrelatedintangibleassetsMember
Namespace Prefix:
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=atml_BonusMember
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=atml_IncometaxesMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=atml_NMIDomain
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=us-gaap_DeferredBonusMember
Namespace Prefix:
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=us-gaap_DeferredTaxAssetDomain
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=us-gaap_GoodwillMember
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BUSINESS COMBINATIONS (Narrative) (Details) (USD $)	0 Months Ended	3 Months Ended		12 Months Ended
BUSINESS COMBINATIONS (Narrative) (Details) (USD $)	Jul. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Business Acquisition [Line Items]
NMI potential earn-out	$ 30,000,000atml_NMIpotentialearnout
Earn-out on acquisition date	400,000atml_Earnoutonacquisitiondate
Goodwill		188,554,000us-gaap_Goodwill		191,088,000us-gaap_Goodwill
Acquisition-related charges		4,403,000	1,628,000
NMI [Domain]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	139,600,000
Goodwill	86,123,000
NMI goodwill - Deductible for Tax	55,200,000
Acquisition-related charges				2,500,000
Goodwill [Member]
Business Acquisition [Line Items]
Goodwill, Purchase Accounting Adjustments				1,900,000
income taxes [Member]
Business Acquisition [Line Items]
Goodwill, Purchase Accounting Adjustments				300,000
Deferred Tax Asset [Domain]
Business Acquisition [Line Items]
Goodwill, Purchase Accounting Adjustments				1,600,000
Deferred Bonus [Member]
Business Acquisition [Line Items]
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed				5,300,000
bonus [Member]
Business Acquisition [Line Items]
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed		1,600,000
acquisition related intangible assets [Member]
Business Acquisition [Line Items]
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed		$ 1,700,000