Risk Management and Use of Derivative Financial Instruments (Narratives) (Details)	3 Months Ended			3 Months Ended		3 Months Ended
	Mar. 31, 2013 USD ($) property	Mar. 31, 2012 USD ($)	Dec. 31, 2012 USD ($)	Mar. 31, 2013 Interest Expense USD ($)	Mar. 31, 2013 Cash Flow Hedging USD ($)	Mar. 31, 2013 Interest rate cap USD ($)	Mar. 31, 2012 Interest rate cap USD ($)	Mar. 31, 2013 Interest rate cap Unconsolidated Member USD ($)	Mar. 31, 2012 Interest rate cap Unconsolidated Member USD ($)	Mar. 31, 2013 Interest rate cap 1-Month LIBOR Derivatives Not in Cash Flow Hedging Relationships	Mar. 31, 2013 Interest rate cap 3-Month LIBOR Derivatives Not in Cash Flow Hedging Relationships	Mar. 31, 2013 Forward contracts USD ($)	Mar. 31, 2013 Forward contracts EUR (€)	Mar. 31, 2013 Forward contracts Derivatives Not in Cash Flow Hedging Relationships Noncontrolling Interest USD ($)	Mar. 31, 2013 CPA: 16 - Global USD ($) property	Mar. 31, 2013 CPA: 16 - Global Hotel property	Sep. 28, 2012 CPA 15 property
Summary of Derivative Instruments
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ (387,000)	$ (335,000)						$ 100,000	$ 100,000
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	3,073,000	291,000				(3,000)	0	100,000	100,000
Notional Amount													47,669,000	33,500,000
Fair Value	262,000				(5,025,000)	0						(68,000)		3,600,000
Debt instrument interest rate at end of period										4.20%	2.80%
Maximum credit exposure	300,000
Derivative Fair Value, Gross Liability	20,700,000
Aggregate termination value of derivatives in liability position	21,800,000
Derivative instruments gain loss reclassification from OCI to income, to be transferred				2,100,000
Concentration Risk Percentage	10.00%
Percentage Geography															18.50%
Assets	$ 4,609,614,000		$ 4,609,042,000												$ 3,300,000,000
Number of real estate properties	422														494	2	305