Schedule III - Real Estate and Accumulated Depreciation - Narratives (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule III, Real Estate and Accumulated Depreciation
Accumulated amortization (finite lived intangible assets)	$ 707,914	$ 539,495
Finite-lived intangible liabilities, gross	148,949	146,085
Accumulated amortization (intangible liabilities)	51,703	40,593
Real estate under construction	39,800
Federal income taxes	7,100,000
Lease intangibles
SEC Schedule III, Real Estate and Accumulated Depreciation
Finite-lived intangible liabilities, gross	165,700
Accumulated amortization (intangible liabilities)	51,700
Lease intangibles
SEC Schedule III, Real Estate and Accumulated Depreciation
Finite lived intangible assets, gross	1,853,471	1,803,755
Accumulated amortization (finite lived intangible assets)	$ 699,651	$ 534,427