Real Estate (Summary of Real Estate Subject to Operating Leases) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property Subject to or Available for Operating Lease [Line Items]
Real estate subject to operating leases, gross	$ 7,855,114	$ 7,236,237
Less accumulated depreciation and amortization	(1,009,374)	(874,519)
Real estate subject to operating leases before work in process	6,845,740	6,361,718
Work in progress - improvements	8,017	41,920	$ 24,057
Accounted for using the operating method, net of accumulated depreciation and amortization	6,853,757	6,403,638
Revenue recognized	309	1,411	$ (12)
Balance of accrued rental income	25,387	25,916
Allowances	1,842	1,936
Land and improvements
Property Subject to or Available for Operating Lease [Line Items]
Land and improvements	2,374,005	2,282,919
Buildings and improvements
Property Subject to or Available for Operating Lease [Line Items]
Buildings and improvements	5,477,479	4,948,057
Leasehold interests
Property Subject to or Available for Operating Lease [Line Items]
Leasehold interests	3,630	5,261
Work in progress - improvements
Property Subject to or Available for Operating Lease [Line Items]
Work in progress - improvements	8,017	41,920
Properties under construction
Property Subject to or Available for Operating Lease [Line Items]
Land and improvements	$ 5,571	$ 25,799