Net Investment in Sales-Type Leases - Long Term Net Investment in Sales Type Leases (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Dec. 31, 2016
Capital Leased Assets [Line Items]
Net minimum lease payments to be received	$ 32,214	$ 33,591
Less: Unearned interest income portion	(2,506)	(2,763)
Net investment in sales-type leases	29,708	30,828
Less: Short-term portion	(10,534)	(10,243)
Long-term investment in sales-type leases, net	19,174	20,585
Collective allowance for credit losses	$ 200	$ 300
Minimum
Capital Leased Assets [Line Items]
Terms of sales-type leases (generally up to five years in length)	1 year
Maximum
Capital Leased Assets [Line Items]
Terms of sales-type leases (generally up to five years in length)	5 years

Capital Leases, Net Investment in Sales Type Leases, Unearned Interest Income Portion

No definition available.

Name:	omcl_CapitalLeasesNetInvestmentinSalesTypeLeasesUnearnedInterestIncomePortion
Namespace Prefix:	omcl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Lessor Leasing Arrangements, Capital Leases, Term of Contract

+ References

No definition available.

+ Details

Name:	omcl_LessorLeasingArrangementsCapitalLeasesTermofContract
Namespace Prefix:	omcl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

A valuation allowance for receivables due to an Entity for more than one year from the balance sheet date that are expected to be uncollectible.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(4))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5074-111524

+ Details

Name:	us-gaap_AllowanceForDoubtfulAccountsReceivableNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_CapitalLeasedAssetsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The net amount due within one year of the balance sheet date or the normal operating cycle, if longer, consisting of: (a) minimum lease payments on sales type leases and (b) unguaranteed residual value; less: (i) executory costs, (ii) unearned income, and (iii) the accumulated allowance for uncollectible minimum lease payments.

+ References

+ Details

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

- Definition

The net amount due after one year of the balance sheet date or beyond the normal operating cycle, if longer, consisting of: (a) minimum lease payments on sales type leases, and (b) unguaranteed residual value; less: (i) executory costs, (ii) unearned income, and (iii) the accumulated allowance for uncollectible minimum lease payments.

+ References

+ Details

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

- Definition

The net investment in sales type leases as of the balance sheet date consisting of: (a) minimum lease payments on sales type leases and (b) unguaranteed residual value; less: (i) executory costs, (ii) unearned income, and (iii) the accumulated allowance for uncollectible minimum lease payments.

+ References

+ Details

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

- Definition

Amount of remaining payments as of the balance sheet date that lessees are obligated to make or can be required to make under sales-type leases, including any guarantee of residual value and executory costs. The amount also includes any guaranteed rental payments by an unrelated third-party provided that are financially capable of making such payments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=25496975&loc=d3e45377-112738

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 25
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=7661868&loc=d3e34102-112682

+ Details

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

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: