Organization and Summary of Significant Accounting Policies Significant supplier disclosure (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Supplier Concentration Risk [Member]	Sep. 30, 2011 Supplier Concentration Risk [Member]
Unusual Risk or Uncertainty [Line Items]
Purchases from significant supplier	$ 6.3	$ 4.9	$ 17.8	$ 16.1

Purchases from significant supplier - pruchasses during period from most significant supplier mentioned in Supplier Dependence section of Note 1

No definition available.

Name:	omcl_PurchasesFromSignificantSupplier
Namespace Prefix:	omcl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration