Transactions with Norfolk Southern Railway Company (Allocation of Estimated Fair Values of Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 01, 2019	Dec. 31, 2018
Intangible assets:
Total assets	$ 4,251,193		$ 4,146,296
1200 Peachtree
Tangible assets:
Land and improvements		$ 19,495
Building		62,836
Tangible assets		82,331
Intangible assets:
In-place leases		9,969
Intangible assets		9,969
Total assets		$ 92,300