Capital units number of units sold to investors

No definition available.

Name:	stem_CapitalUnitsNumberOfUnitsSoldToInvestors
Namespace Prefix:	stem_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Capital units price per unit

+ References

No definition available.

+ Details

Name:	stem_CapitalUnitsPricePerUnit
Namespace Prefix:	stem_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Class Of Warrant Or Right Exercise Period Of Warrants Or Rights

+ References

No definition available.

+ Details

Name:	stem_ClassOfWarrantOrRightExercisePeriodOfWarrantsOrRights
Namespace Prefix:	stem_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Class of warrant or right number of warrants or rights expired

+ References

No definition available.

+ Details

Name:	stem_ClassOfWarrantOrRightNumberOfWarrantsOrRightsExpired
Namespace Prefix:	stem_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Institutional Investors Units Common Stock Shares Issued Per Unit

+ References

No definition available.

+ Details

Name:	stem_InstitutionalInvestorsUnitsCommonStockSharesIssuedPerUnit
Namespace Prefix:	stem_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Institutional Investors Units Warrants Issued Per Unit

+ References

No definition available.

+ Details

Name:	stem_InstitutionalInvestorsUnitsWarrantsIssuedPerUnit
Namespace Prefix:	stem_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of warrant exercised.

+ References

No definition available.

+ Details

Name:	stem_NumberOfWarrantExercised
Namespace Prefix:	stem_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Warrant Unit Sold

+ References

No definition available.

+ Details

Name:	stem_NumberOfWarrantUnitSold
Namespace Prefix:	stem_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Public Offered Units Series Warrants Issued Per Unit

+ References

No definition available.

+ Details

Name:	stem_PublicOfferedUnitsSeriesWarrantsIssuedPerUnit
Namespace Prefix:	stem_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

- Definition

Expiration date of warrants

+ References

No definition available.

+ Details

Name:	stem_WarrantExpiration
Namespace Prefix:	stem_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Warrant Issued For Warrant Exercised

+ References

No definition available.

+ Details

Name:	stem_WarrantIssuedForWarrantExercised
Namespace Prefix:	stem_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Warrants Expiry Month And Year

+ References

No definition available.

+ Details

Name:	stem_WarrantsExpiryMonthAndYear
Namespace Prefix:	stem_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

Cost to investors of each class of capital shares or other capital units.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.6-04.16(b)(1))

-URI http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996

+ Details

Name:	us-gaap_CapitalUnitsTotalCostToInvestors
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

+ Details

Name:	us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_ClassOfWarrantOrRightLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of securities into which each warrant or right may be converted. For example, but not limited to, each warrant may be converted into two shares.

+ References

No definition available.

+ Details

Name:	us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(i)(2))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph i

-Subparagraph 2

-Article 4

+ Details

Name:	us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Cash received on stock transaction after deduction of issuance costs.

+ References

No definition available.

+ Details

Name:	us-gaap_SaleOfStockConsiderationReceivedOnTransaction
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of new stock issued during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

+ Details

Name:	us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=stem_SeriesWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=us-gaap_WarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=stem_DecemberTwoThousandElevenFinancingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=stem_NovemberTwoThousandEightFinancingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=stem_NovemberTwoThousandNineFinancingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Warrant Liability - Additional Information (Detail) (USD $)	1 Months Ended			12 Months Ended			6 Months Ended	1 Months Ended	12 Months Ended
	Jul. 31, 2014	Oct. 31, 2013	Nov. 30, 2008	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Nov. 30, 2009	Dec. 31, 2011
Class of Warrant or Right [Line Items]
Exercise price of warrants	$ 2.17	$ 1.80
Warrants expired unexercised			2014-05
Number of shares issued upon warrants exercise	11,299,435	12,845,500
Outstanding Warrants [Member]
Class of Warrant or Right [Line Items]
Number of shares of common stock in each unit sold to institutional investors	1	1	1
Series A Warrants [Member]
Class of Warrant or Right [Line Items]
Exercise price of warrants				$ 1.40
Proceeds from sale of stock				$ 1,652,000	$ 538,000	$ 3,078,000
Common Stock [Member]
Class of Warrant or Right [Line Items]
Number of securities callable by each warrant or right warrants	0.85	0.5
Number of shares of common stock in each unit sold to institutional investors	1	1
Number of securities callable by warrants				1,180,015
Number of shares issued upon warrants exercise						2,198,571	2,700,000
November 2008 Financing [Member]
Class of Warrant or Right [Line Items]
Number of units sold to investors			1,379,310
Price per unit			14.50
Gross proceeds from units sold to investors			20,000,000
Proceeds from sale of stock			18,637,000
November 2008 Financing [Member] \| Common Stock [Member]
Class of Warrant or Right [Line Items]
Number of securities callable by each warrant or right warrants			0.75
Exercise price of warrants			23.00
Number of securities callable by warrants			1,034,483
November 2009 Financing [Member]
Class of Warrant or Right [Line Items]
Price per unit								$ 12.50
Gross proceeds from units sold to investors								12,500,000
Exercise price of warrants				$ 15.00
Proceeds from sale of stock								$ 11,985,000
Number of units sold to investors								1,000,000
November 2009 Financing [Member] \| Common Stock [Member]
Class of Warrant or Right [Line Items]
Number of securities callable by each warrant or right warrants								0.40
Exercise price of warrants								$ 15.00
Number of securities callable by warrants								400,000
Number of warrants in each unit sold to institutional investors								1
December 2011 Financing [Member]
Class of Warrant or Right [Line Items]
Price per unit									$ 1.25
Number of units sold to investors									10,000,000
Number of Series A warrants in each unit issued in public offering									1
December 2011 Financing [Member] \| Series A Warrants [Member]
Class of Warrant or Right [Line Items]
Number of securities callable by warrants									8,000,000
Warrant expiration				December 2016
Number of warrants exercised				1,180,015	384,534	2,198,571
Number of shares issued upon warrants exercise						2,700,000
December 2011 Financing [Member] \| Series B Warrant [Member]
Class of Warrant or Right [Line Items]
Number of securities callable by warrants									8,000,000
Term of warrant									90 days
Warrant expiration				2012-May-02
Number of warrants exercised						2,700,000
Number of warrants expired				5,300,000
December 2011 Financing [Member] \| Common Stock [Member]
Class of Warrant or Right [Line Items]
Number of securities callable by each warrant or right warrants				1
Number of shares issued upon warrants exercise					384,534	2,700,000
Number of shares issued upon warrants exercise				1,180,015	384,534	2,198,571
December 2011 Financing [Member] \| Common Stock [Member] \| Series A Warrants [Member]
Class of Warrant or Right [Line Items]
Exercise price of warrants									$ 1.40
December 2011 Financing [Member] \| Capital Units [Member] \| Series A Warrants [Member]
Class of Warrant or Right [Line Items]
Number of securities callable by each warrant or right warrants									1
December 2011 Financing [Member] \| Capital Units [Member] \| Series B Warrant [Member]
Class of Warrant or Right [Line Items]
Number of securities callable by each warrant or right warrants									1