Non-recourse debt (Narratives) (Details) (USD $)	9 Months Ended
Sep. 30, 2013	Dec. 31, 2012
Additional Debt Disclosures
Non-recourse mortgage loans	$ 178,200,000
Refinanced debt	9,700,000
Debt, weighted average interest rate	4.70%
Debt instrument terms (years)	10 years 2 months 12 days
Debt instrument, maturity date, range start	Oct. 01, 2013
Debt instrument, maturity date, range end	Feb. 01, 2038
Impact due to change in foreign currency exchange rates	7,000,000
Mortgage notes payable, collateral	2,600,000,000	2,400,000,000
2013 Investments
Additional Debt Disclosures
Non-recourse mortgage loans	36,300,000
2013 Investments \| Self storage
Additional Debt Disclosures
Non-recourse mortgage loans	14,300,000
2013 Investments \| International
Additional Debt Disclosures
Non-recourse mortgage loans	12,200,000
Prior years investments
Additional Debt Disclosures
Non-recourse mortgage loans	115,400,000
Prior years investments \| Self storage
Additional Debt Disclosures
Repayment of debt related to refinancing	$ 13,300,000
Debt, weighted average interest rate	4.90%
Debt instrument terms (years)	10 years 0 months 0 days
Fixed interest rate
Additional Debt Disclosures
Mortgage loan real estate, minimum interest rate	2.00%
Mortgage loan real estate, maximum interest rate	8.00%
Variable interest rate
Additional Debt Disclosures
Mortgage loan real estate, minimum interest rate	2.80%
Mortgage loan real estate, maximum interest rate	6.10%

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The aggregate carrying value of real estate assets posted as collateral for the mortgage loans.

+ References

No definition available.

+ Details

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- Definition

Change in the carrying value of debt due to foreign currency exchange rates.

+ References

No definition available.

+ Details

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- Definition

Latest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

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- Definition

Earliest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

+ References

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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- Definition

The highest stated interest rate within the mortgage loans included in the loan grouping.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 10

-Section S99

-Paragraph 6

-Subparagraph (SX 210.5-04.(c) Schedule IV)

-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-29.3)

-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

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-Publisher SEC

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-Number 210

-Section 29

-Article 12

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph c

-Subparagraph Schedule IV

-Article 5

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- Definition

The lowest stated interest rate within the mortgage loans included in the loan grouping.

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+ Details

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- Definition

Amount of debt for which creditor does not have general recourse to the debtor but rather has recourse only to the property used for collateral in the transaction or other specific property.

+ References

No definition available.

+ Details

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- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

No definition available.

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- Definition

Amount of a short-term obligation that has been excluded from current liabilities in the balance sheet because of a refinancing of the obligation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1927-112601

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