v3.19.1

Organization and Limited Liability Company Matters (Narrative) (Details) - USD ($)			12 Months Ended	111 Months Ended	143 Months Ended
	Jan. 24, 2008	Sep. 26, 2007	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jul. 15, 2008
Business activities, description			equipment financing and acquiring equipment to engage in equipment leasing and sales activities
Business formation date			Jan. 25, 2007
Business formation State			California
Business termination date					Dec. 31, 2030
Public offering of Limited Company Units		20,000,000
Public offering of Limited Liability Company Units, price per unit		$ 10
Sale of Limited Liability Company Units, number of units	120,000
Proceeds from sale of Limited Liability Company Units	$ 1,200,000
Contributions received, net of rescissions and/or redemptions			$ 29,900,000	$ 29,900,000	$ 29,900,000
Reinvestment period				6 years
Minimum [Member]
Amount of aggregate subscriptions for Pennsylvania subscriptions to be released to the Fund	$ 7,500,000
Contributions received, net of rescissions and/or redemptions								$ 7,500,000
Other Members [Member]
Units issued			2,992,482	2,992,482	2,992,482	2,992,482
Units outstanding			2,992,482	2,992,482	2,992,482	2,992,482	2,992,482
Managing Member [Member]
Contributions of capital by initial Members			$ 500	$ 500	$ 500
Units issued			50	50	50

Amount Of Aggregate Capital Account Units Subscriptions

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- Definition

Capital Contributions, Initial

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- Definition

Total units issued during the year due to the sale of units. All members include the managing and other members.

+ References

No definition available.

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- Definition

The number of units sold in a public offering of each class of members' capital account. Units represent shares of ownership of the managing and other members.

+ References

No definition available.

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- Definition

Amount per Limited Liability Company Unit issued.

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- Definition

The cash inflow from the issuance of Limited Liability Company units during the period.

+ References

No definition available.

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- Definition

Proceeds from Sale of Equity Units

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No definition available.

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- Definition

Reinvestment Period

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No definition available.

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- Definition

Number of common units issued of limited liability company (LLC).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70434-108055

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- Definition

Number of common units of ownership outstanding of a limited liability company (LLC).

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- Definition

Description of the day-to-day business function and activities of the limited liability company or limited partnership.

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- Definition

Date the limited liability company (LLC) or limited partnership (LP) will cease to exist, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

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- Definition

Date the limited liability company (LLC) or limited partnership (LP) was formed, in CCYY-MM-DD format.

+ References

No definition available.

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- Definition

State in which the limited liability company or limited partnership was organized.

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ATEL 12, LLC 10-K