Other Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Other Assets.
Deferred rent receivable	$ 42,967	$ 40,038
Initial direct costs	25,698	29,979
Internal-use software	17,611	17,477
Prepaid expense	9,270	6,770
Corporate furniture, fixtures and equipment	5,370	6,408
Deferred financing costs - revolving credit facility	3,098	957
Other	2,892	1,872
Total	$ 106,906	$ 103,501