4. Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Certificates of Deposits [Member] \| Short Term Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cost	$ 2,021	$ 4,020
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(4)	(3)
Fair Value	2,017	4,017
Commercial Paper [Member] \| Short Term Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cost	10,977	31,220
Gross Unrealized Gains	0	26
Gross Unrealized Losses	(9)	(38)
Fair Value	10,968	31,208
Corporate Bond Securities [Member] \| Short Term Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cost	11,178	6
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(29)	0
Fair Value	11,149	6
Corporate Bond Securities [Member] \| Long Term Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cost	18,781	5,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(259)	(75)
Fair Value	18,522	4,925
Mutual Funds [Member] \| Short Term Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cost		219
Gross Unrealized Gains		3
Gross Unrealized Losses		0
Fair Value		222
Mutual Funds [Member] \| Long Term Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cost	485
Gross Unrealized Gains	0
Gross Unrealized Losses	(4)
Fair Value	481
Equity Investments [Member] \| Long Term Investments [Member]
Schedule of Held-to-maturity Securities [Line Items]
Cost	5,675	5,675
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2,729)	(1,539)
Fair Value	$ 2,946	$ 4,136

Amount of investment in debt security measured at amortized cost (held-to-maturity).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

+ Details

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

- Definition

Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

+ Details

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

- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_InvestmentSecondaryCategorizationAxis=us-gaap_CertificatesOfDepositMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentSecondaryCategorizationAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentSecondaryCategorizationAxis=us-gaap_CorporateBondSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=atri_LongTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentSecondaryCategorizationAxis=us-gaap_MutualFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentSecondaryCategorizationAxis=atri_EquityInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: