Accounts Receivable Narrative (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014
Receivables [Abstract]
Accounts receivable, gross, using percentage of completion method	$ 0.6	$ 0.7
Billed contracts receivable, using percentage of completion method	0	0.1
Unbilled contracts receivable, using percentage of completion method	$ 0.6	$ 0.6

Gross amounts due for billed and unbilled services rendered or to be rendered or actions taken or to be taken in accordance with the terms of a legally binding agreement between the Company and, at a minimum, one other party, being accounted for by the Company using the percentage of completion method.

No definition available.

Name:	emkr_AccountsReceivableGrossUsingPercentageOfCompletionMethod
Namespace Prefix:	emkr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant