Real Estate (Real Estate Subject to Operating Leases) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property Subject to or Available for Operating Lease [Line Items]
Land and improvements	$ 2,386,548	$ 2,368,635
Buildings and improvements	5,535,000	5,469,460
Leasehold interests	3,630	3,630
Real estate subject to operating leases, gross	7,925,178	7,841,725
Less accumulated depreciation and amortization	(1,043,855)	(1,005,724)
Real estate subject to operating leases, net, before work in process	6,881,323	6,836,001
Work in progress for buildings and improvements	19,424	8,017
Accounted for using the operating method, net of accumulated depreciation and amortization	6,900,747	6,844,018
Asset under construction
Property Subject to or Available for Operating Lease [Line Items]
Land and improvements	$ 10,846	$ 5,571