Net Investment in Sales-Type Leases allowance credit loss rollforward (Details) (USD $)	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Net Investment in Sales-Type Leases [Abstract]
Allowance for Notes, Loans and Financing Receivable, Current	$ 100,000		$ 100,000			$ 500,000
Allowance for Notes, Loans and Financing Receivable, Noncurrent	100,000		100,000			100,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for credit losses, beginning of period			607,000	284,000	184,000		659,000
Current period provision (reversal)	15,000	4,000	34,000	426,000
Direct write-downs charged against the allowance	0	0	(413,000)	0
Recoveries of amounts previously charged off	(25,000)	(26,000)	(54,000)	(73,000)
Allowance for credit losses, end of period	$ 174,000	$ 637,000	$ 174,000	$ 637,000	$ 184,000		$ 659,000

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A valuation allowance relating to a written agreement to receive money (at a specified future date(s) within one year from the reporting date (or the normal operating cycle, whichever is longer), consisting of principal as well as any accrued interest) for the portion that is expected to be uncollectible.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5074-111524

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 4

-Article 5

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-Name Accounting Standards Codification

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-Section S99

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-Subparagraph (SX 210.5-02.4)

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- Definition

A valuation allowance relating to a written agreement to receive money (at a specified future date(s) more than one year from the reporting date, consisting of principal as well as any accrued interest) for the portion that is expected to be uncollectible.

+ References

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A valuation allowance for financing receivables that are expected to be uncollectible.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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Amount of direct write-downs of financing receivables charged against the allowance.

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-Name Accounting Standards Codification

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- Definition

The sum of the periodic provision charged to earnings, based on an assessment of uncollectibility from the counterparty on account of loan, lease or other credit losses, to reduce these accounts to the amount that approximates their net realizable value.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

-Paragraph 168, 169, 170

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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