Organization and Summary of Significant Accounting Policies Significant supplier disclosure (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Unusual Risk or Uncertainty [Line Items]
Purchases from significant supplier	$ 6.7	$ 5.2	$ 13.9	$ 11.5

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