Discontinued Operations (Narrative) (Details) $ in Thousands			1 Months Ended	12 Months Ended
	Dec. 10, 2014 USD ($)	Oct. 22, 2014 USD ($)	Jun. 30, 2013 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2013 USD ($)	Apr. 17, 2015 USD ($)	Apr. 16, 2015 USD ($)	Jan. 02, 2015 USD ($)	Sep. 17, 2014 USD ($)	Mar. 31, 2013 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Flood-related insurance proceeds				$ 0	$ 0	$ 7,790
Photovoltaics Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill				0	$ 20,384
Digital Products Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset purchase agreement, selling price		$ 17,500
Transaction costs incurred in sale of business				1,600
Asset sale, cash consideration		$ 1,500
Asset sale, promissory note, interest rate, year one		0.05
Asset sale, promissory note, interest rate, year two		0.13
Asset sale, promissory note, principal amount		$ 16,000						$ 15,500	$ 1,500
Accrued interest on note receivable							$ 200
Net assets				13,300
Gain (loss) on disposal of discontinued operation				2,000
Photovoltaics [Member] | Photovoltaics Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset purchase agreement, selling price	$ 150,000									$ 150,000
Net assets sold	60,300
Transaction costs incurred in sale of business	$ 2,700
Gain on sale of business				400
Working capital adjustment				100
Emcore Solar New Mexico [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investment, purchase price											$ 1,500
Suncore Photovoltaic Technology Co., Ltd. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investment, ownership percentage			40.00%
Equity method investment, purchase price			$ 4,800
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Flood-related insurance proceeds						$ 11,200
Discontinued Operations [Member] | Photovoltaics [Member] | Photovoltaics Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of business				$ 56,800
Discontinued Operations [Member] | Suncore Photovoltaic Technology Co., Ltd. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deferred revenue, revenue recognized			3,300
Gain on disposal of investment			$ 4,800