Net Investments in Properties and Real Estate Under Construction (Narratives) (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Acquisition
Acquired finite-lived intangible asset, amount			$ 54,610,000
Acquisition-related cost and fees, capitalized	3,284,000	6,636,000	6,689,000	16,568,000
Acquisition costs, expensed	8,510,000	1,008,000	10,305,000	1,634,000
Assets held for sale	11,896,000		11,896,000		0
Foreign Currency Translation
Change in euro/dollar currency exchange rate percentage			2.30%
Foreign currency exchange rate	1.3525		1.3525		1.3218
Foreign currency translation adjustments	32,477,000	13,905,000	15,614,000	(2,432,000)	13,515,000
Real estate
Acquisition
Investment purchase price	44,400,000		44,400,000
Acquired finite-lived intangible asset, amount			8,100,000
Acquisition-related cost and fees, capitalized			2,200,000
Real estate improvements			5,100,000
Additional funding for BTS placed into service	2,300,000		2,300,000
Assets placed into service	26,100,000		26,100,000
Foreign Currency Translation
Foreign currency translation adjustments			15,200,000
Real estate | Manufacturing and office facility
Acquisition
Investment purchase price	10,900,000		10,900,000
Real estate | Parcels of land
Acquisition
Investment purchase price	18,200,000		18,200,000
Real estate | Automotive dealership
Acquisition
Investment purchase price	15,300,000		15,300,000
Operating real estate
Acquisition
Investment purchase price	28,400,000		28,400,000
Land acquired	5,100,000		5,100,000
Buildings acquired	19,700,000		19,700,000
Acquired finite-lived intangible asset, business combination	3,600,000		3,600,000
Acquisition costs, expensed			600,000
Assets placed into service	12,600,000		12,600,000
Real estate under construction
Acquisition
Acquisition-related cost and fees, capitalized			2,300,000
Additional funding for BTS placed into service	62,243,000		62,243,000		121,003,000
Assets placed into service	38,698,000		38,698,000		142,085,000
Unfunded commitments	70,400,000		70,400,000
Foreign Currency Translation
Foreign currency translation adjustments			(41,000)		91,000
Real estate business combination
Acquisition
Investment purchase price	140,300,000		140,300,000
Land acquired	18,400,000		18,400,000
Buildings acquired	83,200,000		83,200,000
Acquired finite-lived intangible asset, business combination	38,600,000		38,600,000
Acquisition costs, expensed			8,900,000
Real estate business combination | Logisitics facility
Acquisition
Investment purchase price	78,100,000		78,100,000
Real estate business combination | Office facility
Acquisition
Investment purchase price	38,600,000		38,600,000
Real estate business combination | Entertainment complex
Acquisition
Investment purchase price	15,700,000		15,700,000
Real estate business combination | Building with ground lease
Acquisition
Investment purchase price	$ 7,900,000		$ 7,900,000