Non-Recourse and Limited Recourse Debt (Narratives) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 year	Dec. 31, 2011 year
Additional Debt Disclosures
Non recourse debt	$ 469,600,000	$ 234,500,000
Debt, weighted average interest rate	4.30%	5.70%
Debt instrument terms (years)	8.6	10
Non recourse debt assumed	36,700,000	50,400,000
Debt instrument, maturity date, range start	Jun. 30, 2013
Debt instrument, maturity date, range end	Sep. 01, 2031
Impact due to change in foreign currency exchange rates	8,300,000
Mortgage notes payable, collateral	2,400,000,000	1,900,000,000
KBR
Additional Debt Disclosures
Non recourse debt	128,200,000
BCBS
Additional Debt Disclosures
Non recourse debt	92,400,000
Self Storage
Additional Debt Disclosures
Non recourse debt	44,900,000	48,100,000
Wanbishi
Additional Debt Disclosures
Non recourse debt	31,600,000
Agrokor IV
Additional Debt Disclosures
Non recourse debt	21,300,000
Two Polish investments
Additional Debt Disclosures
Non recourse debt	13,800,000
Five domestic investments 2011
Additional Debt Disclosures
Non recourse debt	53,000,000
Five domestic investments 2012
Additional Debt Disclosures
Non recourse debt	84,400,000
Two foreign investments
Additional Debt Disclosures
Non recourse debt	52,900,000
Six domestic investments
Additional Debt Disclosures
Non recourse debt		112,100,000
Four domestic investments
Additional Debt Disclosures
Non recourse debt		60,600,000
UK investment
Additional Debt Disclosures
Non recourse debt		13,700,000
New York Times Company (U.S.)
Additional Debt Disclosures
Non recourse debt		125,000,000
Debt, increase (decrease) borrowing		9,000,000
Debt, noncontrolling interest		4,100,000
Debt, outstanding principal		116,000,000
Debt, variable rate basis		LIBOR
Debt, variable rate spread		2.50%
Cap Rate		6.25%
Metro Investment
Additional Debt Disclosures
Debt, weighted average interest rate		4.18%
Debt instrument terms (years)		5
Non recourse debt assumed		222,700,000
Debt, variable rate basis		Euribor
Debt, variable rate spread		2.15%
2011 Investments
Additional Debt Disclosures
Non recourse debt		160,200,000
2012 Investments
Additional Debt Disclosures
Non recourse debt	$ 349,900,000
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	2.90%
Mortgage loan real estate, maximum interest rate	6.60%