Real Estate (Summary of Real Estate Subject to Operating Leases) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property Subject to or Available for Operating Lease [Line Items]
Real estate subject to operating leases, gross	$ 5,815,108	$ 5,164,322
Less accumulated depreciation and amortization	(620,188)	(508,229)
Real estate subject to operating leases before work in process	5,194,920	4,656,093
Work in progress	61,354	28,908	$ 60,720
Accounted for using the operating method, net of accumulated depreciation and amortization	5,256,274	4,685,001
Revenue recognized	153	1,521	$ (338)
Allowances	3,078	3,086
Balance of accrued rental income	25,529	25,659
Land and improvements
Property Subject to or Available for Operating Lease [Line Items]
Land and improvements	1,922,579	1,776,222
Buildings and improvements
Property Subject to or Available for Operating Lease [Line Items]
Buildings and improvements	3,891,239	3,386,810
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	$ 61,354	$ 28,908