Disclosure of Percentage of Long-lived Assets in United States (Details)	Jun. 30, 2012	Sep. 30, 2011
Long-Lived Assets	92.00%	93.00%

Long-lived Assets, Located in United States, Percentage

No definition available.

Name:	emkr_LongLivedAssetsLocatedInUnitedStatesPercentage
Namespace Prefix:	emkr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant