Real Estate (Summary of Real Estate Subject to Operating Leases) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Property Subject to or Available for Operating Lease [Line Items]
Real estate subject to operating leases, gross	$ 5,460,573	$ 5,198,662
Less accumulated depreciation and amortization	(565,335)	(511,664)
Real estate subject to operating leases before work in process	4,895,238	4,686,998
Accounted for using the operating method, net of accumulated depreciation and amortization	4,935,472	4,715,906
Land and improvements
Property Subject to or Available for Operating Lease [Line Items]
Land and improvements	1,857,051	1,782,719
Buildings and improvements
Property Subject to or Available for Operating Lease [Line Items]
Buildings and improvements	3,602,232	3,414,653
Leasehold interests
Property Subject to or Available for Operating Lease [Line Items]
Leasehold interests	1,290	1,290
Work in progress
Property Subject to or Available for Operating Lease [Line Items]
Work in progress	$ 40,234	$ 28,908