Real Estate Investments - Revenue from External Customers and Long-Lived Assets, by Geographical Areas (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
United Kingdom
Real Estate Investments [Line Items]
Entity wide revenue percentage	22.00%	38.40%	100.00%
Puerto Rico
Real Estate Investments [Line Items]
Entity wide revenue percentage		19.40%
Germany
Real Estate Investments [Line Items]
Entity wide revenue percentage	10.90%
California, USA
Real Estate Investments [Line Items]
Entity wide revenue percentage		14.60%
Texas, USA
Real Estate Investments [Line Items]
Entity wide revenue percentage	10.40%